Time Saved by Driving Faster Calculator
How much time driving faster really saves on a trip, minute by minute.
Good to know. Going 20% faster saves only about 17% of the time, and less once traffic and lights get a say.
How it works
In plain words
Time is distance divided by speed. Work out the trip at both speeds and subtract. Because time falls with one over the speed, each extra km/h or mph saves a little less than the one before.
The formula
time = distance ÷ speed saved = distance ÷ usual − distance ÷ faster share saved = 1 − usual ÷ faster
Worked example
100 km takes 1 h at 100 km/h and 50 min at 120 km/h. Driving 20% faster saves 10 min, 16.7% of the time, and only if you can hold that speed the whole way.
Sources
No outside data or rates: this is plain arithmetic.
2 automated tests check its answers on every change.
About the time saved by driving faster calculator
Driving faster feels like it saves a lot of time, but the arithmetic is less generous. Time is distance divided by speed, so the savings shrink as the speed rises: on a 100 km trip, going from 100 to 120 km/h saves 10 minutes, but from 120 to 140 km/h saves only about 7.
And that is the best case, at the faster speed from start to finish. Real trips include towns, junctions, traffic and roadworks, where everyone drives at the same speed whatever their plans. On most journeys the actual saving is a few minutes at most.
The costs grow the other way. Fuel use rises steeply above about 90 km/h (55 mph), because air resistance grows with the square of the speed, and the energy in a crash and the distance needed to stop grow even faster. Speeding fines and points come on top.
This calculator is for curiosity and planning, not for choosing a speed: drive at the limit and the conditions. For a full trip with breaks, use the road trip time calculator; for fuel, the fuel cost calculator.
Questions people ask
How much time do you save driving 10 km/h faster?
On 100 km, going from 100 to 110 km/h saves about 5½ minutes, and from 120 to 130 km/h about 4.
Is speeding worth the time saved?
Rarely. The saving is minutes on most trips, while fuel use, stopping distance and the risk in a crash rise steeply.
Why does driving 20% faster save less than 20% of the time?
Because time is distance divided by speed: 1 ÷ 1.2 is 0.833, so you save 16.7%.