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About this tool
Convert km/h, mph, knots, m/s, ft/s and Mach, with reaction and braking distance for the same speed.
This converter turns one vehicle speed into km/h, mph, knots, metres per second, feet per second and Mach at once, using the exact SI definitions — 1 mile is 1609.344 m, 1 nautical mile is 1852 m and 1 foot is 0.3048 m. It then applies the standard road-design stopping model to the same speed: reaction distance is speed multiplied by reaction time, and braking distance is v² ÷ (2 × 9.80665 × (µ + grade)). Drivers, riders, fleet trainers and students get both the unit answer and the real-world distance that speed needs.
Open Speed Unit Converter Vehicle on AltFTool — it loads instantly in your browser.
Paste or upload your source content.
Choose the target format or conversion mode.
Copy or download the converted result.
Uses the legally defined metre values for mile, nautical mile and foot, not rounded factors.
Shows reaction and braking distance beside the converted number so the speed means something.
Switch between dry asphalt, wet, gravel, snow and ice, and set an uphill or downhill grade.
100 km/h is 62.14 mph. The conversion is exact: divide by 1.609344, because one international mile is defined as 1609.344 metres.
About 126 metres on dry asphalt using a 2.5 second reaction time — roughly 69 m covered while the driver reacts and 56 m of actual braking. On wet asphalt the braking part alone grows to about 87 m, because braking distance rises with the square of speed and falls with the friction coefficient.
A knot is one nautical mile per hour, and a nautical mile is 1852 metres — originally one minute of latitude — so 1 knot is 1.852 km/h. That is why marine and aviation charts, which are laid out in degrees of latitude, use knots rather than km/h.
No, it roughly quadruples it. Braking distance is proportional to the square of speed, so going from 50 to 100 km/h multiplies the braking part by four, while the reaction part only doubles. This is an estimate for a car in good condition; a loaded vehicle, worn tyres or a wet road will need more.
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