Solve any speed–distance–time question
Trip planning, homework, 'how long is a marathon at 12 km/h' — one equation, three solvable fields, four speed units.
Tools used in this guide
The job
speed = distance ÷ time covers 'how fast', 'how far', and 'how long' — the same triangle rearranged. The calculator lets you leave any one field empty and solves it in your units, so you do not have to convert first.
Two of three
Enter any two of speed, distance, and time (as h:m:s). Leave the third blank and calculate. Knots and nautical miles are included for boating questions alongside km/h, mph, and m/s.
Worked example
A marathon (42.195 km) at 12 km/h takes 3:30:59 — call it 3½ hours. The same run at 10 km/h is 4:13:10. Going the other way, 45 minutes at 100 km/h covers 75 km — enough to sanity-check a driving plan.
Where it stops
Constant speed only — no acceleration, traffic, or rest stops. Limits keep inputs sane: minutes and seconds under 60, exactly two fields filled. It is arithmetic, not a travel-time prediction.