Trip time:
distance ÷ average speed

How to calculate trip time

Trip time is the distance divided by your average speed. A 420 km journey at an average of 60 km/h takes 7 hours. Both numbers need to be in matching units, kilometres with kilometres per hour, or miles with miles per hour.

The key word is average. Your speed on the road goes up and down, so use the speed you expect to average over the whole drive, including slow towns and busy junctions, not the speed limit on the open stretch.

The trip time formula with examples

Turn decimal hours into hours and minutes

The calculator returns hours as a decimal, and that catches people out. A result of 8.4 hours is not 8 hours 40 minutes. The part after the decimal point is a fraction of an hour, so multiply it by 60: 0.4 × 60 = 24 minutes, which makes 8 hours 24 minutes.

Try another. A trip of 450 km at 55 km/h works out at 8.18 hours. The 0.18 of an hour is about 11 minutes, so the drive takes roughly 8 hours 11 minutes. Likewise 6.5 hours means 6 hours 30 minutes, never 6 hours 50.

Add stops and delays for the real arrival time

The formula gives driving time only. Add time for fuel or charging, meals and rest breaks. On a 420 km drive at 60 km/h, two 20 minute stops add 40 minutes, so the 7 hours becomes 7 hours 40 minutes door to door.

Build in a margin for traffic, roadworks and weather on routes you do not know. If you have to arrive by a set time, calculate with a slightly lower average speed than you hope for. Starting early costs little and gives you spare time.

For a long drive with a driver change, work out each leg separately, since the average speed in a city leg is not the same as on an open highway.

Trip time in everyday planning

Delivery drivers, school-run parents and families heading home for a festival all use the same sum. A courier with 180 km to cover and an average of 45 km/h in mixed traffic needs 4 hours of driving, which decides the time they must leave the depot.

Use it in reverse as well. If you must arrive at 6 pm and the drive takes 4 hours, set off by 2 pm and add your stops on top. Checking the plan with two different average speeds shows how much slack you have.

Common trip time mistakes

• Using the speed limit as the average speed.
• Reading 7.5 hours as 7 hours 50 minutes.
• Mixing kilometres and miles in the same sum.
• Forgetting stops, tolls and border or ferry waiting times.
• Using one average for a trip that mixes city and highway sections.