Speed Distance Time Calculator - mph, km/h & Pace

One triangle, three formulas

Speed, distance, and time are locked together. Speed = distance / time. Distance = speed x time. Time = distance / speed. Know any two and the third is fixed. Pick what you want in the "Solve for" menu, enter the other two, and the calculator does the rest.

Distance can be miles or kilometers. Time goes in as hours plus minutes, so 3 hours 45 minutes is typed as 3 and 45, not 3.45. Behind the scenes the calculator turns that into 3.75 hours. Every result also shows speed in both mph and km/h, and pace as minutes per mile or per kilometer, matching the distance unit you chose.

Conversions use the exact definition: 1 mile = 1.609344 kilometers. No rounded 1.6 shortcut.

Worked example: road trip average speed

You drive 237 miles and it takes 3 hours 45 minutes. Solve for speed: 237 / 3.75 = 63.2 mph. In metric that is 63.2 x 1.609344 = 101.7 km/h. Pace is 60 / 63.2 = 0.95 minutes per mile, about 57 seconds for every mile.

Notice 63.2 is well under a 70 mph speed limit. That is normal. Traffic, on-ramps, and a coffee stop all drag the average down. If you want moving speed only, subtract stop time before entering it. If you want an honest arrival estimate, leave the stops in.

Now flip it. You have 380 miles left and expect to average 65 mph. Solve for time: 380 / 65 = 5.846 hours. The 0.846 is a fraction of an hour, not minutes: 0.846 x 60 = 50.8, so plan on about 5 hours 51 minutes.

Worked example: a 10K run

You finish 10 kilometers in 55 minutes. Enter 10 km and 0 hours 55 minutes, solve for speed. Result: 10 / (55 / 60) = 10.91 km/h, which is 6.78 mph. Pace is 5:30 per kilometer, or 8:51 per mile.

Runners think in pace, not speed, because a watch shows minutes per mile. Cyclists and drivers think in speed. This tool shows both from one entry, so you never have to convert. For race splits and goal times, the dedicated pace calculator goes deeper.

Mistakes that give wrong answers

Treating minutes as decimals. 2 hours 30 minutes is 2.5 hours, not 2.3. This is the single most common error in hand calculations, and it is why the tool takes hours and minutes in separate boxes.

Averaging speeds instead of computing from totals. Drive 60 miles at 30 mph and 60 miles at 60 mph and your average is not 45 mph. The first leg takes 2 hours, the second 1 hour, so it is 120 miles / 3 hours = 40 mph. Always divide total distance by total time.

Mixing units. Kilometers with an mph speed produces nonsense. Pick one distance unit, and let the calculator translate the result into the other.

Reading the pace output

Pace is the flip side of speed: minutes per mile = 60 / mph, and minutes per kilometer = 60 / km/h. At 6 mph, pace is 10:00 per mile. At 12 km/h, it is 5:00 per kilometer. Doubling speed halves pace.

Pace is also the easiest way to sanity-check a trip. At highway speeds a mile takes under a minute, so a 45-mile commute at a 1:00 pace takes 45 minutes. If the calculator says something wildly different, recheck your inputs before you trust the answer.

Where Americans actually use this

Trip planning is the big one. US interstates mostly post 65 to 75 mph limits in rural areas and 55 to 65 mph near cities, but real averages including stops tend to land far lower. Budget the lower number and you arrive on time.

It is also handy for treadmill and bike trainer workouts that display mph, for checking a delivery or trucking schedule, for homework problems, and for converting speeds when you rent a car in Canada or Europe, where signs are in km/h. 100 km/h, a common highway limit abroad, is 62.1 mph.