How to work out speed, distance or time
- Under Find, choose what you want to work out: Speed, Distance or Time.
- Pick km and km/h or miles and mph, then fill in the two boxes that appear. Type a time as hours and minutes, like 2:30.
- Read the answer. Times come out as hours, minutes and seconds, with the same time in decimal hours and in minutes.
Three worked examples
| Find | You know | Working | Answer |
|---|---|---|---|
| Time | 250 km at 90 km/h | 250 ÷ 90 = 2.778 h | 2:46:40 |
| Speed | 250 km in 2:30 | 250 ÷ 2.5 | 100 km/h |
| Distance | 60 mph for 2:30 | 60 × 2.5 | 150 miles |
A time of 2:30 means 2 hours 30 minutes. You can add seconds too, as in 2:30:15. Both numbers in each sum must use the same unit pair, so convert miles to kilometres first if your speed is in km/h. One mile is 1.609344 km.
Decimal hours are not hours and minutes
The time 2.778 hours is not 2 hours 77 minutes. The part after the point is a fraction of an hour, so multiply it by 60: 0.778 × 60 = 46.7 minutes. That is why the result shows 2:46:40 as well as the decimal.
The same trap works in reverse when you type a time. 1 hour 45 minutes is 1.75 hours, not 1.45. Typing it here as 1:45 avoids the problem, because the calculator converts hours and minutes for you.
For a road trip, the answer is driving time at a steady speed. Traffic, fuel stops and breaks add to it, so allow extra on longer journeys.