Mileage Calculator
Calculate your real-world MPG from odometer readings and fuel fill-ups. Track fuel economy, cost per mile, and full-tank range over any distance.
mi
mi
gal
$/gal
gal
Enter your values above to see the results.
Tips & Notes
- ✓Always refill to the pump auto-shutoff point at both the start and end of your measurement — a completely full tank at both points ensures the most accurate MPG reading.
- ✓Track MPG consistently over 3-4 consecutive fill-ups to get a reliable baseline. A single fill-up result can be skewed by unusually efficient or inefficient driving.
- ✓Highway miles produce 20-30% higher MPG than city miles. If your measurement period included both, your result reflects the blended efficiency for that specific mix.
- ✓A sudden MPG drop of 10% or more between fill-ups often signals a maintenance issue: low tire pressure, dirty air filter, worn spark plugs, or a failing oxygen sensor.
- ✓Use the L/100km result when comparing with vehicles from countries that use the metric system — lower values mean better efficiency, unlike MPG where higher is better.
Common Mistakes
- ✗Not filling to the same level at both readings — starting with a half-full tank and topping off at the end makes MPG results unreliable. Always use the pump auto-shutoff at both fill-ups.
- ✗Entering odometer readings in different units — if the start reading is in miles and the end reading is in km (or vice versa), the distance calculation will be wrong by a factor of 1.609.
- ✗Entering the total dollar amount paid instead of gallons — the fuel field requires the volume of fuel added (gallons), not the money spent at the pump.
- ✗Using one fill-up as a permanent baseline — real-world MPG varies with weather, load, driving conditions, and traffic. Average multiple fill-ups for a reliable figure.
- ✗Forgetting that short cold-start trips significantly lower MPG — a 3-mile cold-start trip may achieve only 50% of highway MPG because the engine runs rich until reaching operating temperature.
Mileage Calculator Overview
Tracking your vehicle's actual MPG from odometer readings gives you personalized fuel economy data that EPA estimates cannot provide. Your driving conditions, routes, habits, and vehicle maintenance state all affect real-world efficiency — knowing your actual number enables accurate trip budgeting, vehicle comparison, and early maintenance detection.
MPG from odometer readings:
Distance (mi) = Odometer End − Odometer Start | MPG = Distance / Gallons Used
EX: Odometer start 28,450 mi, end 28,768 mi → Distance = 318 mi. Gallons used = 10.6. MPG = 318 / 10.6 = 30.0 MPG. At $3.50/gal: Cost per mile = $3.50 / 30 = $0.117/mile. Total fuel cost = 10.6 × $3.50 = $37.10L/100km conversion and range calculation:
L/100km = 235.21 / MPG | Range per tank (mi) = MPG × Tank Size (gal)
EX: 30.0 MPG → L/100km = 235.21 / 30.0 = 7.84 L/100km. With 14-gallon tank: Range = 30.0 × 14 = 420 miles. Practical range at ¼-tank reserve = 420 × 0.75 = 315 miles per fill-upMPG benchmarks by vehicle class:
| Vehicle Class | EPA Average MPG | Real-World Typical | Excellent | Annual Cost (15k mi, $3.50) |
|---|---|---|---|---|
| Compact car | 32 MPG | 28-32 MPG | 35+ MPG | $1,641 |
| Midsize sedan | 29 MPG | 25-30 MPG | 32+ MPG | $1,810 |
| Midsize SUV | 26 MPG | 22-27 MPG | 28+ MPG | $2,019 |
| Full-size truck | 19 MPG | 16-21 MPG | 22+ MPG | $2,763 |
| Hybrid sedan | 52 MPG | 46-54 MPG | 55+ MPG | $1,010 |
| Minivan | 24 MPG | 20-25 MPG | 26+ MPG | $2,188 |
| Factor | MPG Impact | Notes |
|---|---|---|
| Air conditioning (90°F+) | −15 to −25% | Higher impact in city driving |
| Cold weather (below 20°F) | −10 to −20% | Short trips more affected |
| Highway speed 75+ mph | −15 to −25% | vs. 65 mph optimal |
| Under-inflated tires (−10 PSI) | −3 to −4% | Check monthly |
| Roof rack (empty) | −2 to −8% | Aerodynamic drag |
| 100 lbs extra cargo | −1 to −2% | More impact on small cars |
| Dirty air filter | −5 to −10% | Replace every 15-30k miles |
| Worn spark plugs | −4 to −8% | Replace per manufacturer schedule |
Frequently Asked Questions
Note the odometer reading when you fill up completely. Drive normally. At the next fill-up, record the new odometer reading and the gallons pumped. Subtract the start reading from the end reading to get miles driven, then divide by gallons used. Example: odometer went from 42,150 to 42,468 (318 miles), used 10.6 gallons → MPG = 318 ÷ 10.6 = 30.0 MPG. Always fill to the same level (auto-shutoff) at both points for accuracy.
Compact cars and sedans: 30-40 MPG combined is good; 38+ is excellent. Midsize sedans: 28-35 MPG is average; 35+ is efficient. Midsize SUVs: 22-28 MPG is typical. Full-size trucks and large SUVs: 15-22 MPG is standard. Hybrids: 40-60 MPG combined. Plug-in hybrids: 45-65 MPGe combined. Compare your real-world MPG against both your vehicle's EPA rating and the average for your vehicle class. A gap of more than 15% below EPA suggests a maintenance issue or driving pattern worth addressing.
Several factors cause fill-to-fill MPG variation. Route mix — more highway vs. city — is the largest. Temperature: cold weather reduces MPG 10-20% due to rich cold-start mixtures, increased rolling resistance, and denser air. Cargo weight: adding 100 lbs reduces MPG by about 1-2%. AC use: summer AC reduces MPG 5-25%. Driving behavior: aggressive acceleration and hard braking in city traffic reduces MPG 10-40% versus smooth driving. These variations are normal — average 4-6 consecutive fill-ups for a stable baseline.
Divide 235.21 by your MPG. Examples: 25 MPG = 9.41 L/100km; 30 MPG = 7.84 L/100km; 35 MPG = 6.72 L/100km; 40 MPG = 5.88 L/100km. To convert L/100km to MPG, divide 235.21 by the L/100km value. Note that the relationship is inverse: improving from 20 to 22 MPG saves 1.07 L/100km, while improving from 40 to 42 MPG saves only 0.28 L/100km — even though both are the same 2 MPG improvement. This is why fuel efficiency gains at low MPG are disproportionately valuable.
MPG is one of the most sensitive early indicators of mechanical issues. A clogged air filter reduces MPG by 5-10% and is a $20 fix. Worn spark plugs reduce MPG by 4-8% and affect combustion quality. A failing oxygen sensor can reduce MPG by up to 40% and will eventually trigger the check engine light. Low tire pressure (10 PSI below spec) reduces MPG by 3-4%. By tracking MPG at every fill-up in a simple log or app (Fuelly, GasBuddy), you can detect these issues months before they cause obvious symptoms, often preventing more expensive failures.
Range per tank = MPG × tank capacity in gallons. Example: 30 MPG × 15-gallon tank = 450-mile maximum range. In practice, drivers refuel when the gauge reaches ¼ tank for safety buffer, so practical range is 75-80% of maximum: 450 × 0.75 = 338 miles between fill-ups. Your vehicle's dashboard range estimate uses a rolling average of recent MPG — it is more accurate over long trips and less accurate after a driving pattern change (e.g., after highway driving, it overestimates city range). Your observed MPG from this calculator is more reliable for planning purposes.