Speed Distance Time Calculator

How to use

1. 1Pick what to find: Find speed, Find distance, or Find time. The form shows the two inputs you need to fill in.
2. 2Type the known values and pick a unit for each. Distance supports km, miles, meters, feet, yards, and nautical miles. Speed supports km/h, mph, m/s, ft/s, and knots. Time accepts HH:MM:SS, hours, minutes, or seconds.
3. 3Read the primary answer in the unit you picked, and the full conversion table for every common unit of the unknown quantity.
4. 4Click any quick example (road trip, cyclist, marathon, boat) to load a worked scenario, Clear inputs to start over, or Copy summary to grab the full result as plain text.

About this tool

Speed Distance Time Calculator solves the classic relationship distance = speed × time for any one unknown given the other two. Pick Find speed to enter a distance and a time and read the average speed (distance ÷ time). Pick Find distance to enter a speed and a time and read how far you travel at that pace (speed × time). Pick Find time to enter a distance and a speed and read how long the trip takes (distance ÷ speed). Each input has its own unit selector, so distance can be entered in kilometers, miles, meters, feet, yards, or nautical miles; speed can be entered in kilometers per hour, miles per hour, meters per second, feet per second, or knots; and time can be entered as HH:MM:SS, plain hours, plain minutes, or plain seconds. Internally every value is normalized to SI base units (meters, seconds, meters per second) before the math runs, so the answer is consistent no matter which units you mix. The result panel shows the primary answer in the unit you picked above, plus a full conversion table for the unknown quantity so the speed value appears at once in km/h, mph, m/s, ft/s, and knots, the distance value in km, miles, meters, feet, yards, and nautical miles, and the time value as HH:MM:SS plus hours, minutes, and seconds. Useful for road trip planning (how long does 300 miles at 55 mph take), running and cycling planning (how far can I ride at 25 km/h for 2 hours), marine navigation (50 nautical miles at 18 knots), bike commute time, drone or RC flight estimates, physics homework, kinematics problems, and any back of the envelope estimate that turns on the SDT triangle. The math is exact (no rounding before the final display), and everything runs locally in the browser so the numbers you type are not sent anywhere.

Free to use. Works in your browser. No signup, no login.