Speed Converter

Speed converter for km/h, mph, m/s, ft/s, and knots

A speed converter helps you translate one speed unit into another without mental math. This matters more than people think. Car dashboards, road signs, fitness apps, aircraft and marine navigation, and engineering references often use different units. If you mix them up, you do not just get the wrong number, you make the wrong decision. This calculator converts between kilometers per hour (km/h), miles per hour (mph), meters per second (m/s), feet per second (ft/s), and knots (kn).

To use it, enter your speed value, choose the unit you currently have, and choose the unit you want. Click convert and you will get a main conversion plus a breakdown into all the supported units. The main conversion is the one you asked for. The breakdown is there to reduce friction when you are comparing multiple references, like a speed limit in km/h vs a vehicle specification in mph, or a wind speed given in knots vs a running pace tool that expects km/h.

Under the hood, the calculator converts your input to a neutral base unit first, then converts from the base unit to the unit you selected. In this calculator the base is meters per second. This approach is more reliable than trying to maintain dozens of direct unit-to-unit formulas. It also makes it easier to add more units later without increasing error risk.

Assumptions and how to use this calculator

• This tool converts speed units only. It does not estimate travel time, acceleration, or distance.
• The conversion uses standard international definitions (for example, 1 mph and 1 knot have fixed relationships to meters per second).
• Results are rounded to 2 decimals for readability. If you need high precision, use the unrounded value in a dedicated engineering tool.
• Enter non-negative values. Negative speeds are uncommon in real-world use and usually indicate direction, which is outside a unit converter’s scope.
• Knots are treated as nautical miles per hour, which is the standard meaning of knots in navigation and weather reporting.

Common questions

Why does the result show only two decimals?

Two decimals is a practical balance for most users. Speed readings from dashboards, GPS, and weather reports are rarely precise beyond that. If you are doing a design calculation where rounding matters, treat the displayed value as a rounded summary and compute with more precision in your engineering workflow.

What is the difference between km/h, mph, and m/s?

They measure the same thing: distance per unit time, but in different measurement systems. km/h is common in most countries for road travel. mph is common in the United States and a few others. m/s is common in physics and engineering because it fits cleanly into SI units.

When should I use knots?

Knots are widely used in marine and aviation contexts, and also in weather reporting for wind speeds. If you are reading marine forecasts, nautical charts, aircraft performance tables, or wind data at airports, you will frequently see knots.

What if I only know an approximate speed?

That is fine. The calculator does not require perfect inputs. Use the best estimate you have. The conversion is exact given the input, so the only uncertainty is in your estimate. If the number is rough, treat the output as rough too.

Why do my converted values differ slightly from another website?

Small differences usually come from rounding. Some tools show more decimals or round at a different step. If you compare values, check how many decimals are displayed and whether the tool rounds intermediate results. For normal use, these differences are not meaningful.