Time equals distance over speed
Divide the miles by your average speed in mph and you get hours. The awkward part is the decimal: 4.62 hours is not 4 hours 62 minutes. Multiply the 0.62 by 60 to get the minutes, so 4.62 hours is 4 hours 37 minutes.
Drive time at a glance
| Distance | at 55 mph | at 65 mph | at 75 mph |
|---|---|---|---|
| 100 miles | 1 h 49 m | 1 h 32 m | 1 h 20 m |
| 250 miles | 4 h 33 m | 3 h 51 m | 3 h 20 m |
| 500 miles | 9 h 5 m | 7 h 42 m | 6 h 40 m |
| 1,000 miles | 18 h 11 m | 15 h 23 m | 13 h 20 m |
These are wheels-turning times only. They do not include stops, and they assume you hold that average the whole way — which highway driving rarely does.
Why the real trip takes longer
- Your average is below the limit. Merging, towns, construction and traffic pull the true average down. A "70 mph" highway trip often averages 60 to 65.
- Stops are not in the formula. Fuel, meals and rest breaks add up. Plan a break every 2 hours or 100 to 150 miles, and pad the total by about 15 to 20 percent.
- Weather cuts speed. Rain, snow or fog can drop your average 20 to 30 percent, which stretches the trip by the same share.
Turning it around
The same relationship gives you the other two figures. Know the distance and time and you get your true average speed; know the speed and time and you get how far you will reach.
Common questions
How do I work out drive time?
Divide the distance by your average speed. 300 miles at 60 mph is 5 hours; 300 miles at 65 mph is about 4 hours 37 minutes. To turn a decimal into minutes, multiply the fractional part by 60.
Should I use the speed limit as my average speed?
No. Real average speed is lower than the limit once you count on-ramps, towns, traffic and slowdowns. On a long highway trip, 60 to 65 mph is a more honest planning figure than the posted 70.
How much time should I add for stops?
Roughly 15 to 20 percent on a long day. Fuel, food and rest breaks add up, and safety guidance is a break every 2 hours, so a 10-hour drive realistically runs closer to 12.
