Speed, Distance, Time Formula
Distance = Speed × Time
Speed = Distance / Time
Time = Distance / Speed
Unit conversions:
1 mph = 1.60934 km/h = 0.44704 m/s
1 mile = 1.60934 km = 1609.34 m
Speed Distance Time Calculator
Calculate speed, distance, or travel time using D = S × T. Leave one field empty and fill in the other two to find the missing value. Supports mph, km/h, m/s, and multiple time formats.
Speed / Distance / Time Calculator
Leave the value you want to find empty.
Frequently Asked Questions
How do I convert mph to km/h?
Multiply mph by 1.60934 to get km/h. For example, 60 mph = 60 × 1.60934 = 96.56 km/h. To convert km/h to mph, divide by 1.60934 (or multiply by 0.62137).
What is average speed vs instantaneous speed?
Average speed is total distance divided by total time for a journey. Instantaneous speed is the speed at a specific moment (like what your speedometer shows). This calculator computes average speed.
The three forms
Speed = distance ÷ time
Distance = speed × time
Time = distance ÷ speed
All three are the same relationship rearranged. Knowing any two gives the third.
Unit consistency is everything
The single biggest source of error. If speed is in miles per hour, time must be in hours — not minutes.
Example: travelling 45 minutes at 60 mph. Using 45 gives a nonsensical 2,700 miles. Converting first: 45 ÷ 60 = 0.75 hours, so 60 × 0.75 = 45 miles.
| Minutes | Hours |
|---|---|
| 15 | 0.25 |
| 20 | 0.33 |
| 30 | 0.5 |
| 45 | 0.75 |
| 90 | 1.5 |
Average speed is not the average of speeds
Drive 60 miles at 30 mph then 60 miles at 60 mph. The average speed is not 45 mph.
The first leg takes 2 hours, the second takes 1. That is 120 miles in 3 hours, so the average is 40 mph. You spend longer at the slower speed, so it carries more weight.
Average speed is always total distance divided by total time, never the mean of the individual speeds.
Speed vs velocity
In physics, speed is a scalar — magnitude only. Velocity is a vector and includes direction. Drive a complete loop and return home: your average speed was substantial, but your average velocity is zero, because displacement was zero.