Speed Calculator
Speed is distance divided by time, and almost every error in the topic comes from the units rather than the division. Get the units consistent and the arithmetic is a single line.
Speed in kilometres per hour
75
- The same speed in miles per hour
- 46.6028
- Pace in minutes per kilometre
- 0.8
- The distance in miles
- 93.2057
Values update as you type. This calculator covers the single scenario its formula assumes — see Common Mistakes for what it leaves out.
The formula this calculator uses
s = d / t
- s
- Speed — distance covered per unit of time
- d
- Distance travelled along the path
- t
- Time taken, in decimal hours
- 3.6
- Kilometres per hour in one metre per second
How to check the result by hand
- 1
Decide which two quantities you have and which one you want
The three forms of the relationship are s = d / t, d = s x t and t = d / s. Read the question and identify whether you are given distance and time, speed and time, or distance and speed, because that determines which form to use. A problem that supplies a speed and a duration wants distance, not speed.
- 2
Put the distance and the time into matching units
Convert before dividing. If the distance is in kilometres and the time in minutes, either turn the time into hours or the distance into the unit that matches minutes. Writing the units beside each number makes a mismatch obvious, and catching it here is far cheaper than catching it after the division has produced a plausible but wrong figure.
- 3
Convert the time to decimal hours
Divide the minutes by 60 and add the whole hours. One hour 45 minutes is 1 + 45/60 = 1.75 hours; one hour 30 minutes is 1.5 hours, never 1.30. This step is where the most common silent error enters, so perform it deliberately rather than reading the time as it is written on the page.
- 4
Divide the distance by the time
150 kilometres in 2 hours is 150 / 2 = 75 kilometres per hour. Keep full precision through the division and resist rounding until the end. The result carries the units of distance over time, so the arithmetic itself tells you what the number means and which unit it belongs to.
- 5
Check the magnitude and convert if needed
75 kilometres per hour is 20.8333333 metres per second and 46.6028394 miles per hour, with a pace of 0.8 minutes per kilometre. Sanity-check the size against experience: a motorway speed should land near 100 kilometres per hour, a walking speed near 5. If the number is off by a clean factor of sixty, the units were mismatched.
For worked examples, common mistakes and the limits of this formula, read the full How To Calculate Speed page.