Odometer gas mileage log: calculate MPG, L/100 km, and cost per mile

Turn consecutive odometer fill-ups into fleet efficiency metrics

At each full-tank fill-up, subtracting the previous odometer reading from the current reading gives recorded miles driven: CurrOdo - PrevOdo (42,510 - 42,150 = 360 miles).

Dividing miles driven by gallons pumped gives US MPG (360 / 12 = 30.0 MPG), dividing total fuel cost by miles gives cost per mile (43.20 / 360 = 0.12), and 235.215 / MPG converts US MPG into metric liters per 100 km (7.84 L/100 km).

MPG formula with odometer typo protection

Guard against zero gallons or reversed odometer entries (CurrOdo <= PrevOdo) before dividing.

=IF(OR(C2<=0, B2<=A2), "Invalid", ROUND((B2 - A2) / C2, 1))

Cost per mile and metric L/100 km conversion

Because MPG and L/100 km are inversely proportional, 235.215 / MPG converts between the two in either direction.

=ROUND(D2 / (B2 - A2), 2)

Inputs and interpretation

Use miles and US gallons, not kilometres or imperial gallons, for the 235.215 conversion. Estimate consumption between comparable full-tank fills; partial fills, measurement error and odometer rollover need separate handling. Cost-per-mile and conversion formulas require positive fuel and distance too. For multiple trips, divide total distance by total fuel rather than averaging MPG values.

Further reading

• Microsoft Support — OR function