Introduction: Compare premiums vs deductible + coinsurance (expected annual cost)
Choosing between a low-deductible / higher-premium plan and a high-deductible / lower-premium plan is usually a tradeoff between predictable monthly cost and the risk of a large bill when you file a claim. This page helps you compare two options using a simple, transparent model. You enter the numbers from your quotes (premium, deductible, and coinsurance) plus your best estimate of claim frequency and claim size.
The calculator returns an expected annual cost for each plan. “Expected” means probability-weighted: it is not a guarantee of what you will pay, but a consistent way to compare Plan A and Plan B under the same assumptions. If you want to ignore uncertainty, set Chance of a Claim to 100%. If you want to model a low-likelihood year, set it to something like 10% or 25%.
What you need (and what each input means)
- Annual premium (Plan A / Plan B): total premium paid over a year (not monthly). If you only know monthly premium, multiply by 12.
- Deductible (Plan A / Plan B): the amount you pay before coinsurance applies. In this model it is treated as a per-claim deductible.
- Coinsurance (Plan A / Plan B): the percentage you pay after the deductible. Example: 20% coinsurance means you pay 20% of the remaining covered amount.
- Expected claims per year: how many claims you would file in a typical year if you have a claim year (can be fractional, e.g., 0.5).
- Average claim amount: your estimate of the typical claim size (in dollars). The calculator uses this to estimate how much is above the deductible.
- Chance of a claim this year (%): probability of having a claim year. This scales the expected number of claims: expectedClaims = claims × probability.
Model and formulas used
For each plan, the calculator estimates the out-of-pocket cost per claim as the deductible you actually reach (capped by the average claim amount) plus coinsurance on the remaining amount. Then it multiplies that per-claim cost by the expected number of claims and adds the annual premium.
- Deductible paid per claim:
ded = min(deductible, averageClaimAmount) - Coinsurance paid per claim:
coinsPay = max(0, averageClaimAmount − ded) × coinsuranceRate - Expected number of claims:
expectedClaims = expectedClaimsPerYear × (claimProbability / 100) - Expected annual cost:
annualPremium + expectedClaims × (ded + coinsPay)
The results may also include a break-even claim probability when it can be computed. That is the probability at which both plans have the same expected annual cost, given your other inputs. If the break-even probability is, for example, 35%, then Plan A is cheaper when your claim probability is above 35% and Plan B is cheaper below 35% (assuming the rest of the inputs stay the same).
Assumptions and limitations (important)
- Average-claim approximation: each claim is treated as the same “average claim amount.” Real claims vary and can be skewed by rare large events.
- No out-of-pocket maximum: the model does not cap spending at an out-of-pocket maximum. If your plan has a cap, your worst-case cost may be lower than this model suggests.
- No copays / exclusions / network pricing: these can materially change real costs, especially for health insurance.
- Coinsurance applies only above the deductible: if the average claim is below the deductible, coinsurance contributes $0 in this model.
- Per-claim deductible assumption: the deductible is treated as applying per claim. Some policies use annual deductibles; if so, interpret “Expected claims” as the number of deductible-triggering events and treat results as a rough proxy.
Worked example (realistic numbers)
Suppose you are comparing two plans with these inputs:
- Plan A: premium $1,800/year, deductible $500, coinsurance 20%
- Plan B: premium $1,200/year, deductible $1,500, coinsurance 10%
- Expected claims per year: 1.0
- Average claim amount: $3,000
- Chance of a claim this year: 60%
Plan A per-claim out-of-pocket is deductible min(500, 3000) = 500 plus coinsurance (3000 − 500) × 0.20 = 500, totaling about $1,000.
Expected claims is 1.0 × 0.60 = 0.6, so expected out-of-pocket is 0.6 × 1000 = 600 and expected annual cost is 1800 + 600 = 2400.
Plan B is computed the same way. If Plan B’s expected annual cost comes out below $2,400, it is cheaper under these assumptions; if it comes out above, Plan A is cheaper.
Practical tips for better inputs
If you are unsure about claim frequency or claim size, run at least three scenarios: low, typical, and high. If the “winner” changes across scenarios, the decision is sensitive. In that case, consider your risk tolerance, emergency savings, and the maximum bill you could comfortably pay.
Educational note: this page provides a simplified estimate for comparison and does not constitute financial, medical, or legal advice.
More guidance: interpreting results and making a decision
The output is an expected value: a probability-weighted average. A plan with a lower expected cost can still have a higher worst-case cost. Use the calculator to answer two separate questions:
- Which plan is cheaper on average? Compare the expected annual costs.
- Which plan is safer in a bad year? Consider deductible size, coinsurance, and any out-of-pocket maximums (not modeled here).
If the difference between plans is small, non-price features may dominate: provider network, coverage limits, claim service quality, and whether filing claims affects future premiums. If the difference is large, the numbers can provide a strong starting point for choosing a plan or negotiating coverage.
Scenario ideas to test
- Low-usage year: reduce expected claims and/or claim probability.
- High-usage year: increase expected claims and average claim amount.
- Small claims: set average claim amount below the deductible to see how premiums dominate.
- Coinsurance sensitivity: increase coinsurance to see how quickly costs rise for larger claims.
Common input mistakes
- Entering a monthly premium as an annual premium (or vice versa).
- Using a deductible that is annual when you intend a per-claim deductible (or vice versa). This model treats it as per claim.
- Setting coinsurance as a whole number but forgetting it is a percent (e.g., entering 0.2 instead of 20).
- Using an average claim amount that is unrealistically low/high compared to your typical claims.
Decision checklist (beyond the expected cost)
A deductible decision is rarely only about the average. Before you finalize a plan, walk through this checklist and write down your answers. Doing this once makes it easier to compare options during open enrollment or when renewing auto/home coverage.
- Cash-flow readiness: Could you pay the higher deductible tomorrow without borrowing? If not, the “cheaper” plan on average may still be stressful.
- Worst-case exposure: What is the largest plausible claim amount for your situation? (For health, think hospitalization; for auto, think collision; for homeowners, think water damage.)
- Out-of-pocket maximum: If your policy has one, compare it across plans. A higher premium may buy a lower cap, which can matter in a bad year.
- Claim behavior and future premiums: Some lines of insurance can raise rates after claims. If you tend to avoid small claims, a higher deductible can align with that behavior.
- Coverage details: Network, exclusions, endorsements, and service quality can outweigh small expected-cost differences.
How to read the break-even probability
When the calculator shows a break-even claim probability, treat it as a threshold for your uncertainty. If your personal estimate of having a claim year is above the break-even value, the plan with lower per-claim cost tends to win. If your estimate is below it, the plan with lower premium tends to win. If the break-even value is not shown, it usually means the plans are too similar under your inputs (or the math cannot produce a probability between 0% and 100% for the given numbers).
Mini sensitivity analysis (quick stress test)
A fast way to test robustness is to keep premiums and deductibles fixed and vary only one uncertain input. For example, run the calculator three times with the same plan details but different claim probabilities: 10%, 50%, and 90%. Then repeat with different average claim amounts (for instance $500, $2,000, and $10,000). If one plan wins across most combinations, your decision is less sensitive. If the winner flips often, consider choosing based on risk tolerance and worst-case affordability rather than the single “best” expected value.
Limitations recap
This calculator is intentionally simple so you can compare plans quickly. For health insurance in particular, real costs can depend on negotiated rates, copays, tiered drugs, and annual out-of-pocket maximums. For auto and homeowners, claim history can affect future premiums. Use this tool as a structured estimate, then confirm details in your policy documents.
Glossary (plain-language definitions)
Insurance terms are often used inconsistently across products. This short glossary explains how the terms are used on this page so you can map them to your policy.
- Premium
- The amount you pay to keep the policy active. This calculator uses an annual premium (12 months total).
- Deductible
- The amount you pay before coinsurance applies. Here it is treated as a per-claim amount and capped at the average claim amount.
- Coinsurance
- The percentage of the remaining claim amount you pay after the deductible. Example: 20% coinsurance means you pay 20 cents of each dollar above the deductible.
- Expected value
- A probability-weighted average. It is useful for comparison, but it does not describe the full range of possible outcomes.
- Break-even probability
- The claim probability at which both plans have the same expected annual cost under the current inputs.
Record keeping and repeatable comparisons
If you are comparing more than two options, you can still use this tool effectively. Pick a baseline plan and compare it against each alternative one at a time. Save the results (or copy them using the button) along with the inputs you used. When you revisit the decision later, you can rerun the same scenarios and see how changes in premiums or deductibles affect the recommendation. This is especially helpful when premiums change year to year or when your expected claim frequency changes due to life events.
How to use this calculator
- Enter Annual Premium Plan A ($) using the unit or time period shown by the field.
- Enter Deductible Plan A ($) using the unit or time period shown by the field.
- Enter Coinsurance Plan A (%) using the unit or time period shown by the field.
- Run the calculation and compare the output with a second scenario before acting on it.
Arcade Mini-Game: Insurance Deductible Optimizer Calibration Run
Use this quick arcade run to practice separating useful scenario inputs from common planning mistakes before you rely on the calculator output.
Start the game, then use your pointer or arrow keys to catch useful inputs and avoid bad assumptions.
Status messages will appear here.