Four limits, and the word that decides how they interact
A family health plan carries an individual deductible, a family deductible, an individual out-of-pocket maximum and a family out-of-pocket maximum. Which of them actually applies to a given claim depends on whether the plan's family deductible is embedded or aggregate.
Embedded. Each covered member has their own deductible. Once a member satisfies it, that member moves to coinsurance regardless of what anyone else in the household has spent. Separately, once the family deductible is met in total, every member's deductible is treated as satisfied. So each member's effective deductible is the individual amount, and the family amount is a backstop that helps when several members each spend a little.
Aggregate. There is no individual deductible in practice. The plan pays nothing for anyone until the entire family deductible has been met, from any combination of members. One member with a serious illness therefore works through the whole family deductible by themselves.
On the default figures — a $2,000 individual and $4,000 family deductible — that difference is worth $1,600 to a household where one member spends $8,000 and nobody else spends anything. It is the same plan by every headline number in the summary of benefits.
One protection applies to both designs. Since the 2016 plan year, federal rules require the self-only annual limit on cost sharing to apply to each individual enrolled in family coverage, even where the deductible is aggregate. So a single member's cost sharing always stops at the individual out-of-pocket maximum, however the deductible is structured. That is the floor under the aggregate design, and it is worth knowing about because it is not obvious from the plan documents.
Why this needs a simulation rather than a formula
For one person the arithmetic is a two-line expression: pay in full to the deductible, then a percentage, capped at the maximum. For a family it is not, because the accumulators interact.
Each member has their own deductible accumulator and their own out-of-pocket accumulator. Both feed a family accumulator. Whichever cap binds first stops the charge, and which one that is depends on how much each member has spent and on the order the claims were processed. A $5,000 claim in March and a $5,000 claim in November land differently on the accumulators than two $5,000 claims in the same week.
This calculator resolves that by processing every member's spending concurrently in small increments, so the answer does not depend on an arbitrary ordering. That is a modelling choice, and it is the right one for planning: it matches what happens when a household's care is spread across the year, and it gives the same family total as any other ordering. Where ordering does matter is the split between members, which can move by a few hundred dollars either way — enough to notice on a statement, not enough to change a plan decision.
What each dollar of spending does, in order. First it tests whether the applicable deductible is met — the member's own on an embedded plan, the family's on an aggregate one. If not, the dollar is paid in full and added to both the member's and the family's deductible accumulators. If the deductible is met, the member pays the coinsurance rate. Then the resulting charge is trimmed by whichever of the individual and family out-of-pocket maximums has less room left. Note that only cost sharing counts toward the out-of-pocket maximum — premiums do not, and neither do out-of-network balance bills, which the balance billing calculator works through separately.
Worked example: the same $8,000 under both designs
Your plan has a $2,000 individual deductible, a $4,000 family deductible, 20% coinsurance, a $6,000 individual out-of-pocket maximum and a $12,000 family maximum. One member has $8,000 of allowed charges this year. Nobody else uses any care.
Under an embedded design:
- Deductible. The member pays their own $2,000 in full. The family deductible now stands at $2,000 of $4,000.
- Coinsurance. $8,000 − $2,000 = $6,000 remains, at 20% = $1,200.
- Total. $2,000 + $1,200 = $3,200, well under the $6,000 individual cap.
- The plan pays $8,000 − $3,200 = $4,800.
Under an aggregate design:
- Deductible. Nothing is paid by the plan until the full $4,000 family deductible is met, and this member is the only one spending, so they pay all of it.
- Coinsurance. $8,000 − $4,000 = $4,000 remains, at 20% = $800.
- Total. $4,000 + $800 = $4,800.
- The plan pays $8,000 − $4,800 = $3,200.
The aggregate design costs this household $1,600 more, and the difference is exactly the extra deductible ($2,000) less the coinsurance saved on that same $2,000 ($2,000 × 20% = $400): 2,000 − 400 = 1,600. That identity holds while the member is above the family deductible and below the individual cap, which is the regime most single-sick-member years fall into.
Now change the spending pattern. Member 1 spends $3,000 and member 2 spends $1,500. Under the embedded design, member 1 pays their own $2,000 deductible plus 20% of the remaining $1,000 = $2,200; member 2 never reaches their own $2,000 deductible, so they pay all $1,500. The family deductible accumulator holds $2,000 + $1,500 = $3,500, still $500 short of $4,000. Family total: $3,700. Under the aggregate design the family works through $4,000 of deductible between them and then pays 20% of the last $500 = $100, for $4,100. Aggregate is more expensive again, by $400.
How to read the result
The cost of the next $1,000 is the number to act on. If it is $1,000, you are below a deductible and any elective care is fully out of pocket. If it is $200, you are in coinsurance at 20%. If it is $0, someone has hit a cap and further care that year is free at the point of use. That third case is the one worth planning around: if a member reaches their individual out-of-pocket maximum in September, the deferred procedure, the second opinion and the dental-adjacent surgery all become free until 31 December.
Watch for a member approaching their individual cap. On an embedded plan a member's costs stop at the individual maximum regardless of the family position, so a household with one seriously ill member may find the family maximum irrelevant. On the default individual cap of $6,000 against a $12,000 family cap, a single member can never consume more than half the family limit.
The remaining family deductible tells you what a second member's care will cost. If member 1 has satisfied their own deductible on an embedded plan but the family deductible is still $2,000 short, member 2's first $2,000 of care is paid in full — not at coinsurance. Households routinely misread this and budget at the coinsurance rate.
Plan-year timing matters more than anything on this page. Every accumulator resets on the plan year, which is not always the calendar year. Care in the last week of December and the first week of January can fall either side of a full reset, and if you are close to a cap that difference is worth thousands. Check the plan-year start date, and check whether your plan has a carry-over provision for fourth-quarter deductible spending — some do.
Everything here assumes in-network care. Out-of-network services usually have their own separate deductible and maximum, which accumulate independently and are often far higher or absent entirely. Spending in one bucket does nothing for the other.
One member's cost, embedded against aggregate
| That member's allowed charges | Embedded — member pays | Aggregate — member pays | Aggregate costs more by |
|---|---|---|---|
| $1,000 | $1,000 | $1,000 | $0 |
| $2,000 | $2,000 | $2,000 | $0 |
| $4,000 | $2,400 | $4,000 | $1,600 |
| $6,000 | $2,800 | $4,400 | $1,600 |
| $10,000 | $3,600 | $5,200 | $1,600 |
| $14,000 | $4,400 | $6,000 | $1,600 |
| $20,000 | $5,600 | $6,000 | $400 |
| $22,000 | $6,000 | $6,000 | $0 |
| $30,000 | $6,000 | $6,000 | $0 |
The gap is $0 below the individual deductible, widens to a constant $1,600 through the middle of the range, and closes again once both designs reach the $6,000 individual cap — aggregate at $14,000 of spending and embedded at $22,000. Aggregate is never cheaper than embedded for a single member, because the family deductible is never smaller than the individual one.
Details that catch families out
- Not knowing which design you are on. It is one word in the summary of benefits and it is worth $1,600 in the example above. High-deductible plans paired with an HSA are frequently aggregate; traditional PPOs are usually embedded.
- Assuming the family maximum protects one sick member. It does not, and it does not need to — the individual maximum applies to each person on family coverage, so a single member's exposure is the smaller figure.
- Forgetting that premiums are outside the cap. The most a plan can cost you in a year is twelve months of premium plus the out-of-pocket maximum, which the total annual cost calculator computes directly.
- Mixing in-network and out-of-network spending. They run on separate accumulators. Reaching the in-network maximum does nothing for an out-of-network claim, and balance bills count toward no cap at all.
- Using billed charges instead of allowed amounts. Accumulators track the negotiated allowed amount. Entering the provider's list price will overstate every figure on this page substantially.
- Missing the plan-year reset. Accumulators zero on the plan year, which may not be the calendar year. Elective care scheduled a week either side of the reset can differ by thousands when a cap is close.
- Copays that do not touch the deductible. Many plans apply copays toward the out-of-pocket maximum but not toward the deductible. Check which, because it changes how fast the deductible clears.
What the federal cost-sharing limits actually cap
The Affordable Care Act sets an annual maximum on cost sharing for non-grandfathered plans, adjusted each year and published by the Department of Health and Human Services in the Notice of Benefit and Payment Parameters. It applies to in-network essential health benefits only. Four things sit outside it: premiums; out-of-network care, unless the No Surprises Act applies to the claim; services the plan does not cover at all; and any amount above the allowed charge. Since the 2016 plan year the self-only limit must be embedded for every individual enrolled in family coverage, whatever the deductible design — that rule closed a gap in which one member of a family on an aggregate plan could be exposed to the whole family maximum. Grandfathered plans, short-term limited-duration policies and health care sharing ministries are not subject to any of this, which is the main reason a plan can advertise a low premium and carry an unbounded liability.
Using this at open enrolment, and during the year
At open enrolment, the deductible design belongs in the comparison alongside the premium and the headline deductible. Two plans with identical printed numbers can differ by more than a thousand dollars for a household whose spending is concentrated in one member, and by nothing at all for a household whose spending is spread evenly. Run your own family's pattern through both designs before choosing. Then take the results into the total annual cost calculator, which adds the premium and finds where two plans swap ranking, and the HDHP versus PPO comparison if one of the options is a high-deductible plan.
If a high-deductible plan is on the table, price the health savings account before dismissing it. The employer's contribution is a direct reduction in that plan's cost, and the tax treatment on your own contributions is worth your marginal rate plus payroll tax on every dollar. The HSA long-term value calculator quantifies both, and an aggregate deductible that looks punishing on paper is frequently the cheaper plan once the account is counted.
During the plan year, re-run this page whenever a large claim lands. The two things to watch are a member approaching their individual cap and the family deductible approaching zero, because both change what the next dollar of care costs. And if you are leaving the plan mid-year, remember that accumulators do not travel: a new plan starts every deductible and every maximum at zero, which is why a job change in October can be expensive for a household that has already met its limits. Continuation coverage keeps the same plan and the same accumulators — the COBRA premium calculator prices that option against a marketplace plan.