Five ways to say how fast, one table that shows them all
Speed refuses to standardise. Roads speak in miles or kilometres per hour depending on the country, science and athletics speak in metres per second, ballistics and older engineering in feet per second, and the sea and sky in knots. This converter takes any speed in any of the five and shows it in all five at once, because the follow-up question is always another unit. At the default, 60 mph is 96.5606 km/h, 26.8224 m/s, 88 ft/s and 52.14 knots — a motorway cruise expressed for a runner, a sailor and a physicist simultaneously. Every figure runs through metres per second, the SI unit, using exact factors, so the five answers are guaranteed to agree with each other. For distances themselves, the Length Converter is the sibling tool, and the pre-set pair pages — Kmh to Mph and Mph to Kmh — give the two road conversions their own full tables.
The factors, and the one division worth memorising
The km/h-to-m/s step is the one to internalise, because it is exact and constantly useful: dividing by 3.6 turns a road speed into the scientific unit (100 km/h = 27.78 m/s), and multiplying by 3.6 goes back. Sprinters live on the friendly side of it — a 10-second 100 m averages exactly 10 m/s, which is 36 km/h — while a fastball at 100 mph is 44.7 m/s, and highway speeds in m/s (about 27 at 60 mph) make stopping-distance physics suddenly intuitive: at 27 m/s, a one-second reaction gap is 27 metres of travel before the brakes are even touched. Knots deserve their note: a knot is one nautical mile per hour, and a nautical mile is 1,852 m by definition, tied historically to a minute of latitude — which is why navigation keeps it long after land speeds went metric or imperial.
Quick reference: speeds you already know
Calibration points, all converted exactly: a brisk walk is about 5 km/h — 3.1 mph, 1.39 m/s. A city speed limit of 30 mph is 48.3 km/h. 60 mph, the default here, is 96.6 km/h. A 70 mph motorway limit is 112.7 km/h, and a 100 km/h limit is 62.1 mph — the conversion that catches drivers abroad, since the two numbers look interchangeable and are 7 km/h apart in consequence. A cruising airliner makes about 900 km/h, 559 mph or 486 knots (its true airspeed is quoted in knots at altitude). The speed of sound at sea level is about 343 m/s — 1,235 km/h, 767 mph — which is why m/s stays the working unit wherever speed gets serious: the numbers stay human-sized precisely where mph and km/h balloon into four figures.
Worked example
60 mph = 96.5606 km/h. Worked through the base unit: 60 × 0.44704 = 26.8224 m/s, and 26.8224 × 3.6 = 96.5606 km/h. The same speed is exactly 88 ft/s — a pleasing whole number, because 60 mph is famously a mile a minute — and about 52.14 knots.
How to use this calculator
- Enter the speed.
- Choose the unit it is in and the unit you want.
- Read the headline answer, then scan the all-units table.
- Use the step panel to see the conversion through metres per second for homework or a report.
Wind, water and the Beaufort habit
Weather reports are where most people meet knots and m/s outside a car. Wind speeds in marine forecasts come in knots; in much of Europe's land forecasts, in m/s or km/h; in American forecasts, in mph — the same storm wearing three numbers, which this page translates in one glance. The Beaufort scale, still used at sea, bins wind into forces by its effects (a whole gale, force 10, is 48–55 knots), a reminder that for sailors the number was always secondary to what the sea was doing. If a forecast ever gives you a wind in a unit you do not feel, convert it here and compare it with a speed you do know — 30 knots of wind is motorway-roof-rack serious, about 55.6 km/h — and the abstract figure becomes a decision about whether to sail, ride or rebook.