How do I calculate diminished value on my car?

Use our calculator above. Enter your vehicle's pre-accident fair market value, mileage, and damage severity. The calculator applies both the 17c formula (commonly referenced by insurers) and a market-based estimate. For the most accurate result, use the Kelley Blue Book or NADAguides value for your specific make, model, year, and trim.

Diminished Value Calculator

Commonly referenced formula (Georgia 17c)

Pre-Accident Fair Market Value

Vehicle Mileage

miles

Damage Severity

Moderate (panel replacement)

Structural / Frame Damage

Frame damage significantly increases diminished value

Airbag Deployed

Airbag deployment signals more severe damage

Estimated Diminished Value

$1,000

4% loss in value

Value After Accident

$24,000

Loss Percentage

4.0%

Market Estimate Range

Conservative to optimistic real-world depreciation

Low

$1,750

High

$3,250

17c Formula Breakdown

See exactly how the diminished value is calculated

Step	Value
Pre-Accident Value	$25,000
Base Loss (10% cap)10% of pre-accident value	$2,500
Mileage Multiplier20,000–39,999 miles	×0.80
After Mileage Adjustment	$2,000
Damage Multipliermoderate	×0.50
Diminished Value	$1,000

The 17c formula is a commonly referenced formula that many insurers use to determine diminished value. It applies a 10% cap, then adjusts for mileage and damage severity. Insurer practices vary — the market-based estimate may better reflect your actual loss.

What Is a Diminished Value Calculator?

Understand your car's post-accident worth

10–25%

Typical Value Loss

Market depreciation range

Up to $2,500

17c Base Loss Cap

10% of pre-accident value

Most States

Generally Available

Rules vary — check locally

17c Formula Method

A commonly used insurer method — starts with a 10% cap, then adjusts for mileage and damage severity.

Market-Based Method

A depreciation-rate model based on damage type and severity. Actual loss varies by make, model, and location.

Market estimates suggest a vehicle with an accident history may lose 10–25% of its value even with professional repairs. This calculator quantifies that loss for insurance claims and negotiations.

How the 17c Diminished Value Formula Works

A widely referenced method in three steps

Originating from the State Farm vs. Mabry court case in Georgia, the 17c formula is widely referenced by many insurers when calculating diminished value claims.

Step 1: Base Loss of Value (10% Cap)

Starting Point

Base Loss = Pre-Accident Value × 0.10

The formula caps the loss at 10% of the vehicle's pre-accident fair market value. For a $25,000 car, the base loss is capped at $2,500.

Step 2: Mileage Multiplier

Adjustment

Adjusted Loss = Base Loss × Mileage Multiplier

Mileage Range	Multiplier
0–19,999 miles	×1.00
20,000–39,999 miles	×0.80
40,000–59,999 miles	×0.60
60,000–79,999 miles	×0.40
80,000–99,999 miles	×0.20
100,000+ miles	×0.00

Step 3: Damage Severity Multiplier

Critical Factor

Final DV = Adjusted Loss × Damage Multiplier

×0.25

Minor cosmetic

×0.50

Moderate

×1.00

Severe + structural

Complete 17c Formula:

Diminished Value = (Value × 0.10) × Mileage Multiplier × Damage Multiplier

Market-Based Diminished Value Method

A depreciation-rate model based on damage type and severity

Cosmetic only

5–10%

Paint, bumpers, bolt-on panels replaced with OEM parts

Minor structural

10–15%

Panel replacement, minor frame straightening

Moderate + airbag

15–25%

Structural repair + deployed airbags on vehicle history

Severe + structural

25–40%

Major structural repair, frame machine work, multiple airbags

Tip:

When negotiating a diminished value claim, present both the 17c calculation (to show you know the formula insurers use) and the market-based estimate (to argue for a higher, more realistic amount). Market data from comparable sales is the strongest evidence you can provide.

How to File a Diminished Value Claim

Steps to recover your vehicle's lost value after an accident

Confirm Eligibility

1/5

You must not be at fault for the accident. The other driver's insurance is responsible for your diminished value claim. Some states also allow first-party claims against your own policy.

Document Everything

2/5

Keep all repair estimates, invoices, photos of damage, and the final repair bill. Request that your repair shop notes whether OEM or aftermarket parts were used — OEM repairs result in less diminished value.

Calculate Your Diminished Value

3/5

Use this calculator to get both the 17c formula estimate and the market-based estimate. For claims over $2,000, consider getting a professional certified appraisal — insurance companies take these more seriously.

Submit Your Claim

4/5

Send a written demand letter to the at-fault driver's insurance company. Include your calculated diminished value, supporting documentation, and a deadline for response (typically 15–30 days).

Negotiate

5/5

Expect a low initial offer. Use the market-based estimate and comparable sale data to counter. Claim outcomes vary widely by insurer, damage type, and documentation quality. If negotiations stall, mention filing a complaint with your state insurance commissioner.

Worked Example: 17c Diminished Value Calculation

See the formula in action with real numbers

Scenario

Vehicle

2022 Accord

Pre-Accident Value

$25,000

Mileage

30,000 mi

Damage

Moderate

17c Calculation:

Step 1: Base Loss = $25,000 × 0.10 = $2,500

Step 2: Mileage Multiplier (30K miles) = ×0.80

→ After mileage: $2,500 × 0.80 = $2,000

Step 3: Damage Multiplier (moderate, no structural/airbag) = ×0.50

Final Diminished Value = $2,500 × 0.80 × 0.50 = $1,000

Post-accident value: $24,000 · Loss: 4.0%

The market-based method would estimate $1,750–$3,250 for the same scenario (7–13% depreciation) — significantly higher than the 17c result. This is why it's important to know both numbers before negotiating.

What You Need

Calculator inputs and supporting materials for claims

Calculator Inputs

Pre-accident fair market value (Kelley Blue Book or NADAguides)

Mileage at the time of the accident

Damage severity level (minor, moderate, or severe)

Whether the accident involved structural/frame damage

Whether airbags deployed during the collision

Supporting Documents for a Claim

Repair records, photos, and the final invoice

Comparable sale listings for similar vehicles (with/without accident history)

Estimate Limits and Claim Evidence

Important caveats about these estimates

Not legal or appraisal advice

This calculator provides estimates based on commonly used formulas. Results are for informational purposes only and do not constitute legal advice or a certified appraisal. For claims over $2,000, consider a professional certified appraisal.

17c is a common insurer formula — not universally required

The 17c formula originated from a Georgia court case and is widely referenced by insurance companies. State regulations differ — insurers may use other methods or proprietary formulas. The 17c result is typically a starting point for negotiation, not a guarantee.

Market loss depends on multiple factors

Actual diminished value varies by vehicle make, model, location, repair quality, history report impact (CARFAX/AutoCheck), and comparable sales in your area. The market-based estimate is a heuristic — real-world appraisals consider additional variables.

About These Estimates

Key assumptions behind the numbers on this page

Diminished value estimates rely on the 17c mathematical formula and a market-based depreciation heuristic. Neither accounts for your specific vehicle's condition, local market demand, or insurer negotiation outcomes.

State availability statements reflect general third-party claim frameworks and may not apply to your jurisdiction. Confirm with your state insurance commissioner or a local attorney before filing.

CARFAX / history-report impact estimates draw from resale market surveys and industry analysis. WSJ Buy Side and similar sources discuss how accident history affects vehicle value. Actual impact depends on accident severity, repair quality, vehicle class, and buyer perception in your area.

Claim outcome references describe common negotiation patterns, not guarantees. Settlement amounts depend on insurer practices, documentation quality, policy limits, and applicable state law. For authoritative guidance, consult your state insurance department.

Limitations of the 17c Formula

What the 17c formula misses

The 10% cap is arbitrary

It has no basis in market data and was created for a single court case. Severe damage often causes more than 10% loss.

Mileage is double-counted

Mileage is already reflected in the pre-accident value. Applying a mileage multiplier penalizes the owner twice.

Damage multiplier is subjective

There is no objective standard for assigning 0.25 vs. 0.50 vs. 0.75, allowing insurers to minimize payouts.

Ignores vehicle class and brand

A luxury or rare vehicle loses far more value than an economy car after an accident, but the 17c formula treats them the same.

Ignores history report impact

CARFAX and AutoCheck entries can stigmatize a vehicle in the resale market, causing additional value loss not captured by the formula.

Frequently Asked Questions

Common questions and detailed answers

The 17c formula calculates diminished value in three steps: (1) Take 10% of the pre-accident value as the base loss cap. (2) Multiply by a mileage modifier (1.00 for under 20K miles down to 0.00 for over 100K miles). (3) Multiply by a damage severity modifier (0.25 for minor cosmetic up to 1.00 for severe structural). The name comes from the State Farm vs. Mabry court case in Georgia where it originated.

Based on the market depreciation model used in this calculator, a vehicle may lose 10–25% of its value after an accident, even with professional repairs. Minor cosmetic damage may cause a 5–10% drop, while major structural damage with airbag deployment can reduce value by an estimated 25–40%. Actual loss varies by vehicle make, model, location, and repair quality. Factors that can increase the loss include: structural/frame damage, airbag deployment, vehicle age (newer cars lose more), luxury/exotic vehicle class, and a CARFAX or AutoCheck accident record.

The 17c formula is a fixed mathematical formula commonly referenced by insurers — it caps the loss at 10%, then applies mileage and damage multipliers. It often produces lower numbers. The market-based method uses a depreciation-rate model based on damage type and severity. Market-based estimates are typically higher than 17c results, though actual depreciation varies by vehicle make, model, location, and repair quality. Our calculator shows both so you can compare.

Yes, but in the 17c formula, mileage is applied as a separate multiplier even though it is already reflected in your car's pre-accident value. This 'double penalty' is one of the main criticisms of the 17c formula. Under 17c: 0–19,999 miles gets a 1.00 multiplier (no reduction), 20,000–39,999 gets 0.80, up to 100,000+ miles which gets 0.00 (zero diminished value). In the real market, higher-mileage vehicles do lose less absolute value from an accident, but the 17c formula's steep drop-offs are not market-accurate.

Diminished value claims are generally permitted in most U.S. states, but rules and eligibility vary significantly by jurisdiction. In most states, you file a third-party claim against the at-fault driver's insurance. The 17c formula originated from a Georgia court case (State Farm v. Mabry) and is commonly referenced by insurers, though state regulations vary and may not require its use. A few states (such as Michigan under its no-fault system) have restrictions. Check with your state's insurance commissioner or a local attorney for regulations specific to your jurisdiction. The statute of limitations for property damage claims typically ranges from 2–6 years depending on your state.

The time limit depends on your state's statute of limitations for property damage, which typically ranges from 2 to 6 years from the date of the accident. For example: California (3 years), Texas (2 years), Georgia (4 years), Florida (4 years), New York (3 years). File as soon as possible after repairs are complete — claims are stronger when documentation is fresh and the vehicle can still be inspected.

Damage severity is the most subjective and impactful factor. In the 17c formula, it is the final multiplier (0.00–1.00) applied after the base loss and mileage adjustments. Minor cosmetic damage (scratches, bolt-on panel replacement) gets 0.25. Moderate damage (panel replacement, minor frame work) gets 0.50–0.75. Severe structural damage, especially with airbag deployment, can reach 1.00. In the market-based method, severity also determines the depreciation percentage: cosmetic (5–10%), structural (15–25%), severe with airbag (25–40%).

Yes — an accident appearing on a vehicle history report (CARFAX, AutoCheck) can reduce resale value beyond the physical damage alone. Buyers often avoid vehicles with accident histories or demand discounts. Some industry estimates suggest a CARFAX accident entry alone may reduce value by 5–15%, even for properly repaired vehicles. The 17c formula does not account for this history-report impact. When negotiating a claim, cite the permanent history report as additional justification for a higher settlement.

If the other driver was at fault, their property damage liability insurance pays your diminished value claim. This is a third-party claim. If you were at fault, your own collision coverage typically does not cover diminished value (check your policy — most exclude it). Some states allow uninsured/underinsured motorist property damage coverage to include diminished value. In Georgia, you can file a first-party claim against your own policy for diminished value.

There are two common methods. The 17c formula — widely referenced by insurers — takes 10% of your pre-accident value, then applies a mileage multiplier (1.00 under 20K miles down to 0.00 over 100K) and a damage severity multiplier (0.25 minor to 1.00 severe). The market-based method uses depreciation percentages tied to damage type: 5–10% for cosmetic, 15–25% for moderate with airbag, and 25–40% for severe structural. Use our calculator above to see both estimates side by side.

To calculate manually: determine the pre-accident fair market value, then apply the 17c formula — (Value × 0.10) × Mileage Multiplier × Damage Multiplier. Mileage multipliers range from 1.00 (under 20K miles) to 0.00 (over 100K miles). Damage multipliers range from 0.25 (minor cosmetic) to 1.00 (severe structural with airbag). For a market-based estimate, apply a depreciation rate: 5–10% for cosmetic, 15–25% for moderate, 25–40% for severe structural. Compare both results to strengthen your claim.

After an accident, calculate diminished value by determining your car's pre-accident fair market value, noting the mileage at accident time, and assessing the damage severity. Then apply either the 17c formula (commonly referenced formula: 10% cap × mileage modifier × damage modifier) or a market-based depreciation rate. For example, a $25,000 car with 30,000 miles and moderate damage: $25,000 × 0.10 = $2,500 × 0.80 (mileage) × 0.50 (damage) = $1,000 under 17c, or 7–13% ($1,750–$3,250) via market estimate.

The calculator form needs five inputs: (1) your vehicle's pre-accident fair market value, (2) the mileage at the time of the accident, (3) the damage severity level (minor cosmetic, moderate panel, or severe structural), (4) whether there was structural or frame damage, and (5) whether airbags deployed. When filing an actual claim, also gather repair records, the final invoice, photos, and comparable sale listings for vehicles with and without accident histories — those documents strengthen your negotiation position.

Not necessarily. The 17c formula is the most commonly referenced by insurers, but it has known limitations: the 10% cap is arbitrary, mileage is double-counted, and damage multipliers are subjective. The market-based method often produces higher, more realistic estimates because it accounts for real-world depreciation. For the strongest claim, calculate both — use the 17c result to show you understand the insurer's formula, and present the market-based estimate to argue for a higher settlement.

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Last updated Jun 13, 2026