Car Depreciation by Mileage Calculator

Related Calculators

Table of contents

• How to use
• Common mistakes
• Definitions
• Methodology
• Limitations & assumptions
• Sources

Original price when new ($): The new-car price used as the starting point for value loss.

Car age (years): How long the car has existed since new; decimals are allowed for partial years.

Yearly age value loss (%): The percent of value lost each year before mileage and condition changes.

Normal miles per year (miles): The annual mileage used to decide whether the odometer reading is high or low for the car's age.

Mileage price effect (% per 1,000 miles): The percent change in age-based value for each 1,000 miles above or below normal.

Condition adjustment (%): A manual percent increase or decrease for condition, separate from age and mileage.

Miles above or below normal: Current mileage minus normal mileage for the car's age; positive means above normal, negative means below normal.

Estimated current value: The final estimate after age, mileage, and condition adjustments, floored at $0.

Mistake: Using the loan balance or down payment for Original price when new ($).
Fix: Use the MSRP or original new-car price you want to measure depreciation from.

Mistake: Entering miles driven this year in Current mileage (miles).
Fix: Enter the full odometer reading so Miles above or below normal is based on the car's total use.

Mistake: Treating Normal miles per year (miles) as your personal goal instead of the comparison baseline.
Fix: Use the yearly mileage you consider normal for this car's age and market.

Mistake: Setting Yearly age value loss (%) to 100 or more.
Fix: Use a percent from 0 up to, but not including, 100 so the age-based value can be calculated.

Mistake: Making Mileage price effect (% per 1,000 miles) too large, which can push Estimated current value to $0.
Fix: Lower the mileage effect or compare the result with real listings before using the estimate.

Mistake: Reading Average value lost per mile so far as the cost of the next mile.
Fix: Use it only as a past average; Mileage effect on value is the mileage adjustment used in this estimate.

• This is a planning estimate, not a dealer offer, insurance value, tax basis, or professional appraisal.
• The calculator uses one yearly age value loss rate for the whole period, so it does not model faster first-year loss or model-specific resale curves.
• The mileage adjustment is a simple percent per 1,000 miles above or below normal. Real buyers may react differently to service history, trim, fuel type, accidents, location, and demand.
• Condition adjustment (%) is user-entered. If the condition number is too optimistic or too harsh, the estimate will move by the same direction.
• Estimated current value and Estimated future value are floored at $0 because market value cannot be negative. A $0 result means the assumptions are too harsh for this simple model.
• Average value lost per mile so far is not shown as a meaningful per-mile result when Current mileage (miles) is 0, because dividing by zero is not possible.
• The future estimate keeps the same depreciation rate, normal miles per year, mileage effect, and condition adjustment. It does not predict repairs, accidents, tax credits, inflation, or market shortages.

How the estimate is built

The calculator starts with compound age-based depreciation, then adds a signed mileage adjustment and a signed condition adjustment. Mileage is compared with normal mileage for a car of the same age. Cars with above-normal mileage usually lose value compared with similar lower-mileage cars, so a positive mileage gap creates a negative dollar adjustment.

age_base_value = original_price * (1 - annual_depreciation_rate / 100) ^ car_age_years

normal_miles = car_age_years * expected_miles_per_year

mileage_gap = current_mileage - normal_miles

mileage_value_adjustment = -age_base_value * (mileage_effect_percent_per_1000 / 100) * (mileage_gap / 1000)

condition_adjustment = age_base_value * (condition_adjustment_percent / 100)

raw_current_value = age_base_value + mileage_value_adjustment + condition_adjustment

estimated_current_value = max(0, raw_current_value)

Other results

Value change since original price keeps its sign, so a negative number means the car is estimated to be worth less than the starting price.

value_change_since_original = estimated_current_value - original_price

average_value_lost_per_mile = (original_price - estimated_current_value) / current_mileage

If Current mileage (miles) is 0, the per-mile result is not available because the formula would divide by zero.

Future value

The future estimate repeats the same method after adding the future years and future driving you entered.

future_age = car_age_years + future_years

future_mileage = current_mileage + future_years * future_miles_per_year

future_normal_miles = future_age * expected_miles_per_year

future_gap = future_mileage - future_normal_miles

future_age_base = original_price * (1 - annual_depreciation_rate / 100) ^ future_age

future_mileage_adjustment = -future_age_base * (mileage_effect_percent_per_1000 / 100) * (future_gap / 1000)

future_condition_adjustment = future_age_base * (condition_adjustment_percent / 100)

estimated_future_value = max(0, future_age_base + future_mileage_adjustment + future_condition_adjustment)

future_value_change = estimated_future_value - estimated_current_value

Mini-example

With a $35,000 original price, 5 years of age, 75,000 miles, 15% yearly age value loss, and 11,000 normal miles per year, normal mileage is 55,000 miles and the car is 20,000 miles above normal. Using a 0.5% mileage price effect per 1,000 miles and no condition change, the age-based value is $15,529.69, the mileage effect is -$1,552.97, and the estimated current value is $13,976.72.