How it works
This tool takes two straightforward inputs — the distance you covered and the fuel your vehicle consumed — and returns your real-world fuel economy in miles per gallon. That single ratio becomes the baseline number for budgeting, vehicle comparisons, and expense documentation.
The practical workflow starts at the pump. Fill your tank completely and note the exact odometer reading. Drive normally until your next fill-up, then record the new odometer figure and the gallons required to refill. The difference between those two odometer readings is your distance; dividing it by the gallons purchased yields your efficiency rate.
For reimbursement contexts, the distance itself — not the efficiency — drives the calculation. Business travel expense claims rely on total miles logged multiplied by a published rate, so tracking distance accurately matters more than knowing your burn rate.
The formula
MPG = distance traveled (mi) ÷ fuel consumed (gal)
Worked example
A consultant logs a business trip starting at odometer reading 12,400 and ending at 12,650. The journey covers 250 miles. At the current IRS standard reimbursement rate of 67 cents per mile, the deductible expense claim works out as follows.
Trip distance: 12,650 − 12,400 = 250 mi
Reimbursement amount: 250 mi × $0.67/mi = $167.50
The $167.50 figure represents what the business owes the driver for vehicle wear, fuel, and operating costs during that trip. The consultant submits this amount with the odometer log as supporting documentation.
For fuel economy tracking, if that same 250-mile journey consumed 9.2 gallons at the pump:
Fuel economy: 250 mi ÷ 9.2 gal ≈ 27.2 MPG
| Odometer Start | Odometer End | Distance | Rate | Reimbursement |
|---|---|---|---|---|
| 12,400 mi | 12,650 mi | 250 mi | $0.67/mi | $167.50 |
Tips
Photograph your odometer at the start and end of each business journey — timestamps on the images serve as secondary validation if an expense report gets questioned. For fuel economy tracking, use the same pump at the same station when possible; automatic shutoff triggers vary slightly between pumps, and that variance can distort your MPG reading by 1-2 units on short trips. Always fill until the pump clicks off automatically — do not top off manually.
This calculator provides an estimate of fuel economy and reimbursement amounts, not professional tax or accounting advice. IRS rates change annually, so verify the current standard mileage rate before submitting expense documentation.
When log entries span mixed driving — highway, city, construction detours — the resulting MPG reflects a blended average rather than any single condition. If you need condition-specific figures, record separate entries for each driving type.