Distance divided by speed gives driving time, not journey time, and the gap between the two is where most late arrivals come from. A long drive includes rest breaks, at least one fuel or charging stop, and usually something to eat. This calculator adds those explicitly so the arrival time is one you can actually plan around.
Average moving speed is the other number people get wrong. A motorway limit of 70 mph produces a real average nearer 55 to 60 once junctions, roadworks and traffic are included, and a cross-country route on A and B roads often averages 40 to 45. Using the speed limit as the average is the single biggest source of optimism in a journey plan.
A 320 mile run at 55 mph averages 5.82 hours of driving. Taking a 20 minute break every 2 hours adds 2 breaks, and a 25 minute fuel and food stop brings total stopped time to 65 minutes. The journey therefore takes 6.90 hours door to door, an effective average of 46.4 mph — leaving at 09:00 you arrive at 15:54.
The formula
distance- Route length in miles or kilometres
average speed- Real moving average, not the speed limit
break interval- How often you stop to rest, in hours
stop time- Minutes spent refuelling, charging or eating
How to use this calculator
- Enter the route distance and choose miles or kilometres.
- Enter a realistic average moving speed rather than the speed limit.
- Set how long each rest break lasts and how often you take one.
- Add fuel or charging time and a departure hour to get the arrival time.
Worked examples
320 miles at a 55 mph average
Driving time is 320 ÷ 55 = 5.82 hours. At one 20 minute break every 2 hours that is 2 breaks, plus 25 minutes for fuel and food — 65 minutes stopped. Total 6.90 hours, an effective 46.4 mph.
Optimism versus reality
Assuming the 70 mph limit as an average gives 4.57 hours and no stops — 140 minutes adrift of the realistic figure. Over a 600 mile drive the same error compounds to about 4.4 hours.
How to read your score
Frequently asked questions
What average speed should I use?
For a mostly-motorway route in a car, 55 to 60 mph is realistic against a 70 mph limit. Mixed A-road routes average 40 to 45 mph, and urban legs can drop below 25. Look at what a mapping service predicts for the route and treat that as the moving average rather than the limit.
How often should I really stop?
The standard advice is a fifteen-minute break at least every two hours of driving. Fatigue builds faster than most drivers notice, and the highest-risk window is early afternoon and the small hours. On a long drive, stopping is faster overall than pressing on and slowing down.
Does this work for an electric car?
Yes, if you set the stop time honestly. A rapid charge from 20 to 80 per cent typically takes 25 to 40 minutes, and on a long route you may need two. Enter the total charging time in the stops field and the arrival time will be realistic.
Why is the door-to-door average so much lower than my driving speed?
Because stopped time counts in the total but adds no distance. An hour of stops on a six-hour drive pulls the effective average down by roughly a sixth, which is exactly why journey estimates based on driving speed alone come up short.
Should I add time for the last mile?
Usually yes. Finding the address, parking and unloading routinely take ten to twenty minutes that no route planner counts. Adding that to the fuel and food field is the simplest way to keep the arrival time honest.
Journey time reference
| Distance | At 45 mph | At 55 mph | At 65 mph | Total at 55 mph |
|---|---|---|---|---|
| 50 miles | 1.11 h | 0.91 h | 0.77 h | 1.33 h |
| 100 miles | 2.22 h | 1.82 h | 1.54 h | 2.23 h |
| 150 miles | 3.33 h | 2.73 h | 2.31 h | 3.48 h |
| 200 miles | 4.44 h | 3.64 h | 3.08 h | 4.39 h |
| 320 miles | 7.11 h | 5.82 h | 4.92 h | 6.90 h |
| 450 miles | 10.00 h | 8.18 h | 6.92 h | 9.93 h |
| 600 miles | 13.33 h | 10.91 h | 9.23 h | 12.99 h |
| 800 miles | 17.78 h | 14.55 h | 12.31 h | 17.30 h |
Driving columns exclude stops. The final column adds a 20 minute break for every complete 2 hours at the wheel, plus 25 minutes of fuel and food.