Speed conversion calculators

How to choose and check a conversion

Speed combines distance and elapsed time. Kilometers per hour, miles per hour, meters per second, and knots use different distance units, time units, or both. A knot is one nautical mile per hour and is commonly used in aviation and marine navigation.

These tools convert a stated constant speed. They do not model acceleration, traffic, route length, wind, currents, or stops. To estimate a journey, use distance divided by average speed and account separately for real-world conditions.

Posted limits and vehicle displays are often whole numbers, while scientific readings may need several significant figures. Retain precision for intermediate work, then round the result to match the use and the accuracy of the original reading.

Accuracy and sources

Convertly keeps additional precision during calculation and rounds the display for readability. Match the final precision to the source measurement and the purpose of the answer. See our methodology and source policy for definitions, primary references, limitations, and correction procedures.

Exact definitions, estimates, and rounding

Some unit relationships are exact definitions, while a measured input is still limited by the instrument used to obtain it. A calculator can correctly apply an exact factor without making the original measurement more precise. Keep the original unrounded value, perform the conversion, and round the final result to a level appropriate for the task.

Use the stated formula to check the direction of the conversion. When possible, test a familiar value such as 1, 10, or 100 before relying on an unfamiliar result. For professional, regulated, health, safety, or contractual work, confirm the required convention and rounding rule in the controlling standard or document.