Put two speeds side by side: how much time does the faster option save, how much more fuel does it use – and what does each saved minute cost?
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Distance and speed give the travel time, distance and consumption give the fuel amount, amount and price give the cost. The calculator compares both options and shows which is faster and which is cheaper. Everything is calculated in your browser only.
Travel time = distance ÷ speed. Fuel = distance ÷ 100 × consumption. Cost = fuel × price per litre. Money is calculated in whole cents and rounded only afterwards.
100 km, 100 km/h against 140 km/h, consumption 7.0 against 9.5 l/100 km, price €1.80 per litre: travel time falls from 1:00:00 to 0:42:51, a saving of 17 min 9 s. Fuel rises from 7.0 to 9.5 litres, cost from €12.60 to €17.10. The faster option costs €4.50 more, about €0.26 per saved minute.
The calculation assumes a constant speed over the whole distance. In reality speed and consumption change constantly. Consumption is therefore not estimated from speed but entered by you: it depends on the vehicle, engine, aerodynamics, load, route, weather and driving style. The calculator compares your figures and gives no driving recommendation.
Over 100 km the theoretical travel time falls from 1:00:00 to 0:42:51, a saving of 17 minutes 9 seconds. On longer distances the saving grows in the same proportion.
The calculator divides the extra cost of the faster option by the time saved in minutes. In the example that is €4.50 for 17.14 minutes, about €0.26 per minute. If the faster option is also cheaper, no cost per minute is shown; the saving is shown instead.
It only compares your entries at a theoretically constant speed. Speed limits, traffic, roadworks, weather and breaks are not included. Which speed is permitted and sensible follows from the traffic rules and the road conditions, not from this calculation.