Health Plan Employer Contribution Optimizer

Purpose and model boundary

This calculator compares how an employer splits health plan premiums with its employees over one 12-month plan year. You enter the total monthly premium of each plan and coverage tier, who is enrolled and when, and up to four contribution policies: the baseline you have today and three designs. For each policy the workbook posts, for every enrolled employee and covered month, the employer's contribution and the employee's deduction, and adds them up. The main results are what each policy costs the employer and the employees, how much of the budget it uses and what it saves against the baseline.

A design can also be optimized. The workbook then finds the contribution that keeps employee deductions as close as possible to the target you set for each tier, or that makes the largest monthly deduction as small as possible, without spending more than the budget and within the floors, caps and maximum deductions you set. Every offered optimization is solved exactly inside the spreadsheet, and the result says whether that was proven. The Scenario grid choice adds an 11 by 11 table of what one policy, held fixed, would cost if premiums changed and enrollment shifted toward or away from dependent coverage.

Every figure on this page is computed by the spreadsheet; the page adds nothing to it. The model is educational. It does not quote insurance, does not test the affordability or nondiscrimination rules that apply to employer plans, and does not predict how employees would change plans when contributions change. It is not financial, tax, insurance, benefits or legal advice.

Inputs and units

• Plan year start: the first day of a month from 2000 to 2099. Month 1 of the premiums and of the census starts here.
• Employer budget: the most the employer will spend on premium contributions for the covered months, from 0 to 1,000,000,000 dollars. It is needed only when a design optimizes. Explicit subsidies are reported separately and are not part of it.
• Budget stated as: Annual uses the amount as the plan-year limit; Monthly multiplies it by 12, and months that cost more than one twelfth are flagged, not enforced.
• Payroll frequency: weekly (52), biweekly (26), semimonthly (24) or monthly (12). It is used only to show the deduction per paycheck.
• Plans: up to five, P1 to P5, each with an optional name.
• Premiums: the total monthly premium per contract, employer plus employee share, for each plan, tier and plan month, from 0 to 50,000 dollars in whole cents. A renewal is entered as a different amount from its first month on. A blank is allowed only where nobody is enrolled.
• Tiers: employee only (EE), employee and spouse (ES), employee and children (EC) and family (FAM), each with an optional label, a target monthly deduction and an optional maximum monthly deduction. A blank maximum means no limit; a maximum of 0 means the employer must pay the whole premium.
• Groups: up to ten contribution groups, G01 to G10, such as salaried and hourly, each with an optional name and an optional explicit subsidy per enrolled employee-month.
• Census form: Employee rows or Headcount rows; use one form only, and leave the other empty.
  • Employee rows, up to 10: a synthetic employee ID (a capital letter, then up to 15 capital letters or digits), group, plan, tier, coverage start and end, and whether the employee is eligible for the employer contribution (blank means yes). The same ID may appear on a second row for a mid-year plan or tier change if the two periods do not overlap. The rows can be pasted from a spreadsheet and are put in ID order, then coverage-start order.
  • Headcount rows, up to 20: a group, plan and tier, a first and last plan month from 1 to 12, a headcount from 0 to 100,000, and eligibility. Each row is a cohort, so one row covers any number of employees for any run of months, and a mid-year change takes one more row. Twenty rows hold, for example, two groups with two plans and four tiers plus four change rows; three or more groups with two plans each do not fit.
• Month counted when (employee rows only): a month carries a premium when coverage is in force on its first day, or when the coverage touches any day of it.
• Policies: the baseline and three designs, each with a label, a mode (flat dollars, percent of premium, or two-rate), an action (evaluate the entered values, or optimize; the baseline always evaluates), an objective for an optimized design (target deviation, or lowest maximum deduction), and, for the two-rate mode, the entered rates a and b and their bounds.
• Policy values, for every policy, group and tier: a flat monthly amount with an optional floor and cap, and a rate of premium with an optional minimum and maximum. Each policy reads only the columns of its own mode and action. A blank floor or minimum is 0; a blank cap is the premium and a blank maximum rate is 100%.
• Show results for: the policy the headline figures and the tier chart describe.
• Scenario policy, premium change at the center, premium change step and dependent share step: the scenario grid's fixed policy and its axes.

Money is in US dollars per month or over the covered months, as each label says; rates are percentages of the premium.

Governing relationships

Covered months. Each census row is laid out over the 12 plan months. Under the usual rule a month counts when coverage is in force on its first day; under the alternative it counts when coverage touches any day of it. Coverage outside the plan year is ignored. A headcount row counts its headcount in every month from its first to its last. Rows for the same group, plan, tier and month add up. Ineligible enrollees pay the full premium, count in the premium and employee totals, and are left out of every optimization, the budget and the scenario reallocation.

The three policy modes. On each enrolled employee-month with premium P, and employee-only premium P0 for the same plan and month, the employer's contribution is

flat dollars: E = min(P, amount for the group and tier)

percent of premium: E = rate for the group and tier × P

two-rate: E = min(P, a × P0 + b × max(0, P − P0))

so in the two-rate mode the employer pays share a of the employee-only premium and share b of the extra cost of dependent coverage. One pair of rates applies to every group, both from 0% to 100%, and every premium of a plan must be at least that plan's employee-only premium in the same month. Contributions do not vary by plan.

Posting. The employer's contribution on each employee-month is rounded down to the cent, and the employee's deduction is the premium less that contribution, so the two always add up to the premium exactly and the posted employer cost never exceeds the unrounded one. Every total is a sum of posted cents:

employer cost = sum of employer contributions over the covered months

employee cost = sum of employee deductions over the covered months

budget used = employer cost ÷ plan-year budget

savings against the baseline = baseline employer cost − this policy's employer cost

Explicit subsidies are each group's subsidy times its eligible enrolled employee-months, a separate employer cost. The deduction per paycheck for a group, plan and tier is the enrollment-weighted average monthly deduction of its enrolled months, times 12, divided by the paychecks in a year.

Optimizing for target deviation. The objective is the enrollment-weighted total gap between each eligible employee's monthly deduction and the target for the tier,

objective = sum over eligible employee-months of |deduction − tier target|

subject to each group and tier's contribution staying between its lower bound and its cap, and the employer cost staying within the budget. The lower bound is the floor, raised where needed so that no deduction exceeds the tier maximum. In the flat and percent modes the problem separates by group and tier: without the budget, each cell's best contribution is the weighted median of the contributions that would hit the target exactly, held inside its bounds. If those contributions cost more than the budget, the workbook gives up contribution where it raises the objective least for each dollar saved, segment by segment between the cells' breakpoints, until the cost equals the budget. This is the exact optimum of the problem, and a set of checks on the result certifies it. In the two-rate mode only a and b vary, and the workbook evaluates every corner where two of the problem's constraint and breakpoint lines cross, which is where the optimum must lie; it handles up to 20 distinct enrolled premium amounts.

Optimizing for the lowest maximum deduction (flat and percent modes). The workbook finds the smallest level that every eligible monthly deduction can stay under within the bounds and the budget, by exact interpolation between the sorted breakpoints of the cost of each level, and then returns the cheapest policy that achieves it. This objective is not offered for the two-rate mode.

Infeasibility. A design is infeasible when a lower bound is above its cap or premium, when no two-rate pair meets the rate bounds and the maximum deductions, or when the posted cost of the lowest contributions the design allows is above the budget. The workbook then reports the minimum feasible budget, which is that posted cost, and the shortfall against your budget.

Scenario grid. The scenario policy is held fixed; it is not re-optimized in each cell. Rows change every premium by the center change plus −5 to +5 premium steps, and columns shift each group, plan and month's share of eligible enrollees in the three dependent tiers by −5 to +5 dependent share steps, keeping that pool's own mix of dependent tiers (or the census-wide mix for a pool with no dependents). Shifted headcounts are re-rounded to whole people so each pool keeps its size. Each cell is the employer cost over the covered months; the center cell, with a center change of 0, equals the policy's employer cost exactly.

Calculation sequence

The spreadsheet first checks the inputs and each census row. It then lays every census row over the 12 plan months, posts each policy's contributions and deductions, and adds up the totals. In the Optimize and Scenario grid modes it solves every design whose action is Optimize, and in the Scenario grid mode it then evaluates the 121 cells. A block of consistency checks confirms the arithmetic, including that every posted contribution and deduction add up to the premium, that an optimized design stays within its bounds and the budget and passes its optimality check, and that the grid's center equals the base case, before the status is returned.

Outputs and interpretation

The headline describes the policy you choose under Show results for: the employer's premium contributions, the employees' deductions and the total premiums over the covered months, the share of the budget used, the unused budget and the savings against the baseline, then the explicit subsidies, the employer cost per covered month and the largest monthly deduction. For an optimized design it also shows the objective, its posted value and the continuous optimum it was solved to, the rates a and b of a two-rate design, how the optimizer finished, whether the design was feasible, the minimum feasible budget and, only when infeasible, the shortfall. The Use minimum feasible budget button copies the minimum feasible budget of the policy shown into the budget; it is an annual figure, so use it with the budget stated as Annual.

The policies compared table puts the baseline and the three designs side by side, with each one's employer, employee and premium totals, subsidies, budget use, savings, objective and continuous optimum, largest deduction, rates a and b, the objective change per budget dollar where the budget binds, the lowest maximum deduction level and the optimizer status. Further tables give the contribution or rate of every policy for each group and tier with the constraint that decides it (at the floor, at the maximum deduction bound, at the cap or premium, cut by the budget, at the target median, or no enrollment), enrollment by tier, the deduction per paycheck for every enrolled group, plan and tier under each policy, and the scenario grid. In the grid, the first column gives each row's premium change and the column headings count dependent share steps from −5 to +5, with the shift of each step listed beside the grid. The scenario notes table, in the same layout, says why a cell has no value or how many enrollment pools reached 0% or 100% dependent share there.

Any warnings appear under the results. The model version and the other run details are in the downloaded CSV and JSON files. The per-row census check tables are returned to the API and MCP, and the first problem they find is named in the status.

Under the default inputs, the plan year starts on 1 January 2026 with an annual budget of 70,000 dollars and a biweekly payroll. Two plans, a PPO at 650, 1,300, 1,170 and 1,850 dollars a month and a high-deductible plan at 480, 960, 870 and 1,390, cover ten employees in a salaried and an hourly group, with tier targets of 100, 350, 300 and 550 dollars a month, a family maximum of 750 and a 25-dollar monthly subsidy for each enrolled hourly employee. One employee joins in April, one leaves at the end of August, and one whose coverage starts on 15 March is first billed in April, so the census holds 110 employee-months and 106,940 dollars of premiums. The current flat-dollar policy costs the employer 80,190.00 dollars, 114.6% of the budget. Design 1, flat dollars optimized for target deviation with a 300-dollar employee-only floor, spends exactly the 70,000.00-dollar budget, leaves employees 36,940.00 dollars of deductions and saves 10,190.00 dollars against the current policy. Its total gap from the targets is 5,940.00 dollars, equal to the continuous optimum, and its largest monthly deduction is 550.00 dollars. The salaried employee-only contribution sits at its 300-dollar floor and the salaried employee-and-spouse contribution, 572.50 dollars a month, is the one cut by the budget; its minimum feasible budget is 34,380.00 dollars. The percent-of-premium design spends 69,999.94 dollars and the two-rate design, at a = 76.62% and b = 50.46%, spends 69,999.52, both reaching the same continuous optimum of 5,940 dollars; the two-rate design's largest deduction, 746.43 dollars, stays under the family maximum. Subsidies add 1,325.00 dollars under every policy. The status is OK and every optimized design is OPTIMAL. The first chart stacks the employer and employee cost of each tier for the policy shown. The second puts the four policies side by side against the budget. The third follows each policy's employer cost month by month.

Validation and status logic

The workbook returns one status, chosen in this order: NOT VALID, then INFEASIBLE, then NO SOLUTION FOUND, then CHECK, then OK.

• NOT VALID names the first problem it finds, checked in this order: a plan year start that is not the first of a month; census rows in both forms; no census row in the chosen form; the first failing census row (ID form, group, plan and tier, dates in order, coverage that overlaps an earlier row of the same ID, months from 1 to 12, a whole headcount); a premium that is blank, negative or not in whole cents where someone is enrolled; a two-rate premium below the plan's employee-only premium; a baseline set to optimize; a floor above its cap or a minimum rate above its maximum; a rate outside 0% to 100%; a target, maximum deduction, subsidy or flat amount outside 0 to 50,000 dollars a month; a blank tier target while a design optimizes for target deviation; a blank budget while a design optimizes; the lowest maximum deduction chosen for a two-rate design; more than 20 distinct enrolled premium amounts for a two-rate optimizer; and a scenario premium axis that reaches −100%. NOT VALID is a refusal, not a numeric answer: every figure is withheld.
• INFEASIBLE names the first infeasible design and whether a bound conflicts with a cap or premium, no rates meet the bounds and maximum deductions, or the required minimum contributions cost more than the budget, with the shortfall. Only the shortfall, the minimum feasible budget, the feasibility and finishing explanations and the contributions table with its binding constraints stay on the page.
• NO SOLUTION FOUND reports that an optimizer's certificate failed. It should never occur; it is reported, never shown as OK.
• CHECK accompanies a computed result that needs the stated review: the workbook's own self-check failed; an optimized design is feasible but its optimality check did not pass, so treat it as a good policy rather than a proven best one; an entered flat amount exceeds a premium, so the employer pays the premium there; with a monthly budget, some months cost more than one twelfth of it; overlapping headcount rows were added together; coverage outside the plan year was ignored; ineligible enrollees pay the full premium; or an evaluated policy leaves a deduction above its tier maximum.
• OK otherwise.

The optimizer status is OPTIMAL when every optimized design passed its exactness check, FEASIBLE_NOT_PROVEN or FAILED when one did not, and blank when nothing was optimized or a design was infeasible. The warnings list also reports, without changing the status, scenario cells where some pools reached 0% or 100% dependent share, and a group or plan with no enrollment, which is held at its lower bound.

Assumptions and limitations

• One policy applies to each group and tier, the same for every plan. A two-rate policy uses one pair of rates for every group.
• A monthly premium is billed for a whole month by the month rule you choose; it is never prorated by day.
• A monthly budget becomes one plan-year limit of 12 times the amount; a month above one twelfth is flagged, not limited.
• The employer share is rounded down to the cent on every employee-month, so an optimized design can leave a few cents of the budget unused. The optimality check certifies the unrounded problem, and the posted objective can differ from its continuous optimum by rounding only.
• Targets and maximum deductions are by tier and shared by every group and design; floors and caps are set per design, group and tier.
• The lowest-maximum-deduction design is the cheapest policy that reaches the smallest possible largest deduction.
• The two-rate optimizer handles at most 20 distinct enrolled premium amounts, and the lowest maximum deduction is not offered for the two-rate mode.
• The scenario grid holds the policy fixed and moves enrollment between tiers only; any other change in enrollment is a different census you enter. With few employees most enrollment pools hold one person, so reaching 0% or 100% dependent share is common.
• There is no file import; census rows are pasted.

Restrictions and non-computing states

The calculator enforces its numeric and choice limits before it accepts a result. An eleventh employee row or a twenty-first headcount row is refused before calculation, and a paste over capacity is refused with the row count, never truncated. Rows in both census forms, an empty census, overlapping coverage for one ID and a premium missing where someone is enrolled are refused by the workbook. Designs are optimized only in the Optimize and Scenario grid modes, and the scenario grid is left blank outside the Scenario grid mode.

Errors and warnings

A request rejected by the page's input limits is not a computed result. A transport or service failure, a timeout or a cancelled run cannot establish a fresh workbook answer, and the last result stays on the page marked as out of date. Review the workbook's References and Disclaimer, and your plan documents and carrier rates, before using a result for a real decision.

Sources and further reading

Every premium, census row, target, bound and budget on this page comes from your inputs; the calculator holds no statutory, insurer or market data. The public sources below explain how employer health coverage and employee premium contributions are treated, and where to find public figures on what employers and employees pay. They do not endorse this calculator.

• IRS Publication 15-B (2026), Employer's Tax Guide to Fringe Benefits, "Accident and Health Benefits", explains that the value of accident or health benefits an employer provides can generally be excluded from the employee's wages, and "Cafeteria Plans" explains how a cafeteria plan lets participants receive qualified benefits on a pre-tax basis (retrieved 2026-10-27).
• U.S. Department of Labor, Health Plans and Benefits describes a group health plan as an arrangement set up by an employer, a union or both to provide medical care, and explains that most private-sector plans are covered by ERISA (retrieved 2026-10-27).
• IRS, Questions and Answers on Employer Shared Responsibility Provisions Under the Affordable Care Act explains when an applicable large employer may owe a payment because the coverage it offers is not affordable, a test based on the employee's required contribution for the lowest-cost self-only coverage. This calculator does not run that test (retrieved 2026-10-27).
• Agency for Healthcare Research and Quality, Medical Expenditure Panel Survey Insurance/Employer Component surveys private and public employers on the health insurance they offer, including annual premiums and the annual contributions of employers and employees (retrieved 2026-10-27).
• U.S. Bureau of Labor Statistics, Employee Benefits in the United States reports access to and participation in medical care plans, and its tables give the shares of premiums paid by employers and employees for single and family coverage (retrieved 2026-10-27).

This is an educational model of the contribution policies you enter, not tax, insurance, benefits, payroll or legal advice. It does not test affordability, nondiscrimination or any other rule that applies to employer health plans; check a result against your plan documents, carrier rates and a qualified professional.