What this calculator does
Turn a speed in meters per second into kilometers per hour, or back again, in one step. Meters per second (m/s) is the SI unit of speed, the standard unit scientists use worldwide. Physics textbooks, engineering calculations, wind measurements from weather stations and sports science all use it. Kilometers per hour is the everyday metric unit on road signs and speedometers. Homework problems in particular often give a speed in km/h and expect the answer in m/s, or the other way round.
Both units are metric, so the conversion factor is a clean number. One kilometer is 1,000 m and one hour is 3,600 s. So 1 m/s = 3,600 ÷ 1,000 = 3.6 km/h exactly.
Where it's used
Why this math matters outside the classroom:
- Physics problems. An object moving at 10 m/s travels at 36 km/h, since 10 × 3,600 ÷ 1,000 = 36.
- Sprinting. A sprinter averaging 10.4 m/s is running about 37.4 km/h.
- Wind speed. Weather stations that report wind in m/s show 15 m/s for a 54 km/h wind.
- High-speed trains. A train at 300 km/h is moving about 83.3 m/s.
- Ball sports. A soccer ball kicked at 30 m/s is moving at 108 km/h.
Grade level and standards: Grades 5–6; Common Core State Standards for Mathematics 6.RP.A.3.d. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
How to use it
- Enter a speed in m/s or km/h.
- Choose m/s to km/h, or km/h to m/s.
- Read the result and the working; the table lists typical speeds for the chosen direction.
What the inputs mean
- Value to convert
- A speed in meters per second (for m/s → km/h) or kilometers per hour (for km/h → m/s).
- Direction
- Which way to convert.
Formula and method
km/h = m/s × 3.6 m/s = km/h ÷ 3.6
In one hour an object moving at 1 m/s travels 3,600 m, which is 3.6 km. So multiply m/s by 3.6 to get km/h.
Going back, divide by 3.6. The reverse factor 1/3.6 = 0.2777… repeats, so dividing is cleaner than multiplying by a rounded 0.278.
Worked example
A cyclist rides at 10 m/s. What is that in km/h?
- The factor is exact: 1 m/s = 3.6 km/h.
- 10 × 3.6 = 36.
Result: 10 m/s is exactly 36 km/h.
Understanding the result
No-calculator trick: multiply m/s by 4, then take away a tenth of that. 10 m/s → 40 − 4 = 36 km/h. This is exact, because 4 × 0.9 = 3.6. For km/h to m/s, divide by 4 and add a ninth of that, or just divide by 3.6.
Typical speeds: a brisk walk of about 1.5 m/s is 5.4 km/h; 100 km/h is 27.78 m/s; the speed of sound in dry air at 20 °C, about 343 m/s, is roughly 1,234.8 km/h.
A common exam slip is multiplying when you should divide. A sanity check helps: the km/h number is always bigger than the m/s number for the same speed.
Assumptions and limitations
- Speeds are constant or averaged over the time considered.
- Converts speed only; for acceleration (m/s²) a separate factor of 12,960 per km/h² applies.
Frequently asked questions
Why is the factor exactly 3.6?
An hour has 3,600 seconds and a kilometer has 1,000 meters. 3,600 ÷ 1,000 = 3.6, with no rounding involved.
How do I convert km/h to m/s quickly?
Divide by 3.6. For multiples of 18 it is easy: 18 km/h = 5 m/s, 36 km/h = 10 m/s, 72 km/h = 20 m/s.
Which unit should I use in physics formulas?
Use m/s. Formulas such as kinetic energy (½mv²) or momentum (mv) give SI results only when speed is in meters per second.
How this calculator is checked
Method: 1 km = 1,000 m and 1 h = 3,600 s by definition, so 1 m/s = 3.6 km/h exactly. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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