About this tool
Speed, Distance & Time Calculator is a free, in-browser tool that solves the relationship between speed, distance and time. Pick which quantity to solve for, enter the other two with their units, and the answer appears instantly — also converted into every related unit for convenience. All maths runs locally in your browser.
The relationship is v = d / t, rearranged as d = v · t and t = d / v. To keep unit combinations correct, each input is first converted to SI units — metres and seconds — using fixed factors (mph 0.44704, km/h 0.277778, m/s 1, knots 0.514444 to m/s; mi 1609.344, km 1000, m 1, ft 0.3048 to metres; h 3600, min 60, s 1 to seconds). The result is then converted into the unit you selected.
Use it to plan a journey, check a pace, or convert a speed between systems: switch "Solve for" to Speed, Distance or Time and only the two relevant inputs stay on screen. Enter a distance of zero time and it flags the input rather than dividing by zero.