Property Coinsurance Penalty Calculator
Enter the property value, coinsurance percentage, limit carried, covered loss, and deductible to estimate the insurer payment and any coinsurance penalty.
Estimated insurer payment$70,000.00
- Minimum coverage required
- $800,000.00
- Coinsurance compliance
- 75%
- Additional coverage needed
- $200,000.00
- Payment without coinsurance penalty
- $95,000.00
- Coinsurance penalty
- $25,000.00
- Estimated policyholder share
- $30,000.00
- Requirement status
- Requirement not met
Assumes the entered loss is covered and applies one deductible after the coinsurance ratio.
Actual claim payments can change because of policy wording, sublimits, exclusions, valuation disputes, and insurer rounding.
How to use this calculator
- Enter the property value using the valuation basis required by the policy.
- Enter the coinsurance percentage shown on the declarations page.
- Enter the policy limit carried on the date of loss.
- Enter the covered loss and deductible to see the estimated payment and policyholder share.
How a property coinsurance penalty is calculated
A property coinsurance clause compares the insurance limit you carried with the minimum limit the policy required. If the carried limit is too low, the insurer can reduce payment on a partial loss by the same proportion. The rule is meant to make the premium reflect the amount of property at risk, not only the size of a likely partial claim.
The calculator uses the standard coinsurance formula:
required coverage = property value × coinsurance requirement
compliance ratio = min(1, coverage carried ÷ required coverage)
estimated payment = min(coverage carried, max(0, compliance ratio × covered loss − deductible))
The no-penalty comparison is min(coverage carried, max(0, covered loss − deductible)). The coinsurance penalty is the no-penalty payment minus the estimated payment, never less than zero. The estimated policyholder share is the covered loss minus the estimated insurer payment, so it includes the deductible, any coinsurance penalty, and any loss amount above the policy limit.
What moves the result most
The property value and coinsurance percentage set the minimum coverage required. An 80% clause on a $1,000,000 building requires $800,000 of applicable coverage. Carrying $600,000 produces 75% compliance, so a covered partial loss is reduced to 75% before the deductible is applied.
The carried limit still matters even when the requirement is met. If the adjusted loss is higher than the limit, payment is capped at the limit. A larger covered loss can therefore shift more of the cost to the policyholder even when there is no coinsurance penalty.
What this calculator leaves out
This is a mathematical estimate, not a claim determination or coverage opinion. Policies can use replacement cost, actual cash value, stated amount, reporting forms, margin clauses, agreed-value waivers, blanket limits, sublimits, or special loss-settlement wording that changes the calculation. The tool assumes the entire entered loss is covered, the entered value is the correct valuation basis, and one deductible applies after the coinsurance ratio.
Actual payment can also be affected by exclusions, depreciation, salvage, ordinance or law limits, business income provisions, multiple locations, lender loss-payable terms, appraisal disputes, and claim-specific rounding. Use the result as a check on the formula, then confirm the applicable values and policy language with the insurer, agent, broker, or claims professional.
Worked example
Suppose a building is valued at $1,000,000 and the policy has an 80% coinsurance requirement. The minimum coverage required is $800,000. If the insured carried $600,000, the compliance ratio is $600,000 ÷ $800,000, or 75%.
For a $100,000 covered loss with a $5,000 deductible, the coinsurance-adjusted loss is 75% × $100,000, or $75,000. After the deductible, the estimated insurer payment is $70,000. Without a coinsurance penalty, the payment would have been $95,000, so the penalty is $25,000 and the estimated policyholder share is $30,000.
Common questions
How is a property coinsurance penalty calculated?
The policy limit carried is divided by the minimum limit required by the coinsurance clause. That ratio, capped at 100%, is multiplied by the covered loss before the deductible is subtracted. The penalty is the difference between that adjusted payment and the payment that would have applied without the coinsurance reduction.
What does an 80% coinsurance clause mean?
An 80% clause usually means the insured must carry coverage equal to at least 80% of the property value under the policy valuation basis. If the property value is $1,000,000, the minimum limit is $800,000. Carrying less than that can reduce payment on a partial loss.
Is coinsurance based on replacement cost or market value?
Use the valuation basis required by the policy, which may be replacement cost, actual cash value, or another stated basis. Market value is not automatically the right number for property insurance. The declarations and loss-settlement provisions control which value should be entered.
Does the deductible apply before or after coinsurance?
This calculator applies the deductible after the coinsurance ratio, which is the common presentation of the standard formula. Some policy wording, endorsements, or claim systems may handle rounding and deductible sequencing differently. Check the policy form or ask the claims professional handling the file.
Can a coinsurance penalty apply to a partial loss?
Yes. Coinsurance penalties often matter most on partial losses because the insurer compares the carried limit with the required limit, not just with the claim amount. A policyholder can have a loss well below the policy limit and still receive a reduced payment if the carried limit was too low.
What is an agreed-value waiver of coinsurance?
An agreed-value provision can suspend the coinsurance requirement for a stated period when the insured submits required values and the insurer agrees to them. If the waiver applies to the loss, the standard coinsurance penalty may not apply. The exact effect depends on the endorsement language and whether its conditions were met.