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Medical Bill Calculator: Cost Share and EOB Check

Estimate covered in-network costs from confirmed plan terms, or reconcile EOB patient responsibility with payments, credits and a provider statement.

Use this result well

Inputs that matter
Covered in-network allowed amount, Confirmed cost-sharing rule, Remaining applicable deductible, Patient coinsurance percentage, and 7 more
Output to expect
Estimated patient responsibility, Balance from entered records
  • Check the units and required inputs before comparing results.
  • Keep the assumptions with a copied result so you can reproduce the calculation later.
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Reference & details

How it works

Use the allowed amount and a matching benefit rule

The allowed amount can differ from the provider’s original charge. Select a supported cost-sharing rule only when it matches the service benefit. Coinsurance here means the patient’s percentage. Combined copay-plus-coinsurance rules and multiple services with different rules are outside this model.

Source: CMS: Health insurance terms

Apply the deductible, then the selected cost share

For deductible rules, D is the smaller of the allowed amount and remaining applicable deductible. The remaining amount uses either the patient coinsurance percentage or a fixed copay capped at that remainder. Copay-only ignores the deductible. Inactive inputs are labelled not applicable in result assumptions.

D = min(A, deductible); S = round((A − D) × patient %, cents) or min(A − D, copay); uncapped patient = D + S

Use the remaining applicable limit

The estimate assumes every modeled deductible, copay and coinsurance dollar counts toward the same entered out-of-pocket limit. Enter balances from before the service. It excludes premiums, noncovered charges and balance billing. Ask the plan about family accumulators or exceptions; do not replace an unknown remaining limit with zero.

Patient = min(uncapped patient, remaining limit); plan share = allowed amount − patient

Source: HealthCare.gov: Out-of-pocket maximum

Reconcile matching patient records

An EOB is not a bill and may not reflect payments already made. Match services and dates. Subtract posted patient payments and only additional credits not already included elsewhere. A statement difference or possible credit needs explanation; matching totals do not prove correct claim processing.

Net = EOB patient responsibility − payments − additional credits; balance = max(0, net)

Source: CMS: How to read an EOB

Precision and records

USD amounts accept zero through $10,000,000 with at most two decimal places. Patient percentages accept 0–100 with two decimal places. Amounts use integer cents; coinsurance rounds once to the nearest cent, with a half-cent rounded up. Plan line-level rounding may differ. Save explicitly to this browser, and keep dated supporting documents separately. Exported result details include the assumptions used.

Updated: September 2026

Example Scenarios

Illustrative allowed amount $5,000, remaining deductible $500, patient coinsurance 20%, remaining OOP limit $3,000 and already paid $200.

→ Patient responsibility $1,400; plan share $3,600; estimated remaining balance $1,200.

The same example with only $600 left to the applicable OOP limit.

→ Patient responsibility $600; plan share $4,400; remaining balance $400 after the same $200 payment.

Final EOB patient responsibility $1,400, posted patient payments $200, additional nonduplicated credits $100 and statement balance $1,100.

→ Calculated balance $1,100. The statement matches the entered records; claim accuracy still needs independent verification.

Common Mistakes to Avoid

Subtracting insurance payments again from final EOB patient responsibility

The patient responsibility already reflects the EOB allocation. Reconcile only matching patient payments and additional nonduplicated patient credits.

Using balances already reduced by this claim in estimate mode

Use pre-service deductible and OOP balances for the estimate, or use the final EOB directly in reconciliation mode.

FAQ

In estimate mode, enter the covered in-network allowed amount confirmed by the plan or provider. Original charges can differ. If the allowed amount or benefit rule is unknown, obtain that information before relying on an estimate.

No. This version asks for the patient coinsurance percentage. If the applicable plan pays 80% after the deductible, the corresponding patient share is 20%. Confirm that this is the service’s actual benefit rule.

This model supports deductible then coinsurance, deductible then copay, or copay-only. It does not combine copay and coinsurance. If your benefit uses both or another sequence, request the plan’s service-specific calculation.

Zero means the applicable out-of-pocket limit was already reached before this service. It is not a placeholder for an unknown amount. The model requires all selected cost sharing to count toward that same limit.

No. Check the same services, finalized claim status, payment posting dates, credits and reversals. Ask the provider and insurer to explain any discrepancy. A calculated credit does not guarantee a refund.

Use Save cost estimate or Save bill comparison to store a record in this browser. The two modes have separate histories; earlier calculator records remain separate. CSV result details and Copy Markdown Report include the used assumptions. Keep personal identifiers and diagnoses out of the calculator and retain supporting documents separately.

About Medical Bill Calculator: Cost Share and EOB Check

Start with the right records. The estimate mode uses an allowed amount and confirmed benefit rules for one covered in-network service. The reconciliation mode uses a finalized Explanation of Benefits (EOB) and posted payment records. Both calculate entered amounts; neither verifies coverage or decides what a provider may legally collect.