Solve v = d ÷ t in any direction — speed, distance, or time — with automatic mph, km/h, and m/s conversion. Free and mobile-friendly.
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Choose what to solve for: **speed**, **distance**, or **time**. The triangle of formulas — v = d ÷ t, d = v × t, t = d ÷ v — means any one of the three follows from the other two. Enter the two values you know, set the units (km, miles, or meters for distance; km/h, mph, or m/s for speed; hours for time), and press **Calculate**.
The result appears with the full substitution shown, so a student can copy the working into homework. Time answers are given both as decimal hours and as hours-plus-minutes. **Reset** restores the 150 km / 2 h / 75 km/h defaults.
Because unit conversion happens internally (mph → km/h uses × 1.60934; m/s → km/h uses × 3.6), you can freely mix, say, a distance in miles with a speed in km/h and still get a correct answer.
Who relies on it? Drivers checking trip times, coaches analyzing athlete pace, pilots converting between knots and km/h, logistics planners setting schedules, and students verifying physics homework — anyone who needs the third value when two of speed, distance, and time are known.
Speed is the rate at which distance is covered: meters per second, kilometers per hour, miles per hour. Its stricter cousin velocity adds direction — 60 km/h north is a velocity; 60 km/h alone is a speed. For straight-line travel the numbers coincide, which is why everyday language mixes them.
The SI unit is meters per second (m/s). Road speeds use km/h (or mph in the US/UK): 1 m/s = 3.6 km/h, and 1 mph = 1.60934 km/h. Memorizing 3.6 and 1.609 is the fastest way to move between lab physics and real driving.
Speed is a scalar (magnitude only); velocity is a vector (magnitude plus direction). That distinction matters the moment direction changes: a car circling a track at constant speed has constantly changing velocity.
Engineers also distinguish instantaneous speed — the speedometer reading at one moment — from average speed over a whole trip. Calculus connects them: average speed is total distance over total time, while instantaneous speed is the derivative of position. Traffic apps estimate your arrival from current instantaneous speeds of cars ahead, then blend in historical averages — a live tug-of-war between the two definitions. For everyday trip planning the average is what counts; for safety — braking, cornering, speed limits — the instantaneous reading is the one that matters. Keep both in mind and the speed triangle will never mislead you.
These three are one equation rearranged — the classic “speed triangle” taught in schools: cover the unknown with your thumb and read off the operation. All three assume constant speed; with changing speed they describe average speed over the trip.
Unit discipline is everything: distance in km with time in hours gives km/h. If your time is in minutes, divide by 60 first; if seconds, divide by 3600. The calculator accepts hours directly and converts internally, which removes the most common homework error at the source.
You drive 24 km to work in 35 minutes. What was your average speed? Convert time: 35 ÷ 60 = 0.5833 h. Then v = 24 ÷ 0.5833 ≈ 41.1 km/h. That feels slow for a car — but city traffic with lights makes 40 km/h typical, a good reality check that the math is right.
Reverse it: the return trip at 50 km/h average takes t = 24 ÷ 50 = 0.48 h = 28.8 minutes. Shaving 6 minutes off the commute required raising the average speed by nearly 9 km/h — a vivid lesson in how stubborn travel times are.
A third check: the evening return covers the same 24 km but traffic is lighter, so you hold 60 km/h and arrive in 24 minutes flat. Comparing the three trips — 35, 28.8, and 24 minutes — shows how sensitive arrival time is to small speed changes at city pace, which is exactly why navigation apps re-estimate continuously instead of trusting one calculation.
Minutes as decimals. 1 h 30 min is 1.5 h, not 1.3 h. Divide minutes by 60 — never tack them on as decimals.
Top speed vs. average. Hitting 120 km/h briefly does not make the trip’s average 120 km/h; only total distance ÷ total time does.
mph/km/h mix-ups. A 100 on a US speedometer is mph (≈161 km/h), not km/h. Convert before comparing.
Forgetting stops. Door-to-door time includes red lights and fuel stops; “driving time” alone inflates the average.
Rounding the time first. Rounding 0.5833 h to 0.6 h before dividing shifts the answer by 3% — keep full precision until the end.
Cyclist: 40 km in 1 h 20 min → t = 1.333 h, v = 30 km/h.
Flight: 900 km at 750 km/h → t = 1.2 h = 1 h 12 min.
Sprinter: 100 m in 9.8 s → v = 10.2 m/s = 36.7 km/h.
Road trip: 60 mph for 3.5 h → d = 210 miles = 338 km.
A city requires ambulances to reach any address within 8 minutes. At an urban average of 45 km/h, the reachable road distance is d = 45 × (8 ÷ 60) = 6 km. With a 1.3 detour factor for street grids, stations must sit within about 4.6 km straight-line of every home. Planners run exactly this t = d ÷ v calculation in reverse — starting from the mandated time — to decide how many stations the city needs and where the coverage circles go.
One triangle, three formulas: v = d ÷ t, d = v × t, t = d ÷ v — learn one, derive the rest.
Convert minutes to hours (÷ 60) before touching the formula.
These give average speed unless speed is truly constant.
Speed is scalar; velocity adds direction — they match only on straight paths.
Aviation thinks in knots (nautical miles per hour): 1 knot = 1.852 km/h. A jet cruising at 450 knots covers 833 km/h — and pilots plan with ground speed (relative to Earth) versus airspeed (relative to the air), the difference being wind. A 50-knot headwind quietly adds 20 minutes to a two-hour flight.
Maritime navigation inherited knots from rope-and-log measurements: sailors counted knots in a line paid out over 30 seconds. The tradition survives because a nautical mile equals one minute of latitude — speed and chart distance share the same unit.
Computing borrows speed language for data: Mbps (megabits per second) is a rate exactly like km/h. Downloading a 1 GB file at 100 Mbps takes (8000 Mb ÷ 100 Mbps) = 80 seconds — the same t = d ÷ v with different letters.
Biology marvels at relative speed: a cheetah’s 100 km/h sprint is impressive, but a mite covering 300 body-lengths per second would shame it. Engineers designing tiny robots study these scaled speeds for inspiration.
Everyday driving hides a nonlinear truth: doubling speed from 50 to 100 km/h halves travel time but roughly quadruples braking distance (which grows with v²). Speed limits are set by stopping physics, not travel impatience.
Try these, then check the answers — convert units before computing.
1. 300 km in 3 h 20 min. Average speed? Answer: t = 3.333 h; v = 90 km/h.
2. How long to travel 500 miles at 65 mph? Answer: t ≈ 7.69 h = 7 h 42 min.
3. A swimmer does 1500 m in 25 min. Speed in m/s and km/h? Answer: 1.0 m/s = 3.6 km/h.
4. At 90 km/h, how far in 45 minutes? Answer: t = 0.75 h; d = 67.5 km.
5. Light travels 300,000 km/s. Time to reach the Moon (384,400 km)? Answer: t ≈ 1.28 s.
The speedometer in a car rarely measures speed directly — it counts wheel rotations and multiplies by the tire’s circumference, which is why under-inflated tires make the reading drift. Radar guns use the Doppler shift: radio waves bouncing off a moving car return at a slightly changed frequency, and the shift is proportional to speed. Police lidar does the same with laser pulses and timing.
GPS speed comes from position differences: the receiver notes where you were a second ago and divides by the time. It is remarkably accurate at steady highway speeds but lags in tunnels and jumps when the signal reflects off buildings.
The most precise speed measurements in science use interferometry — counting wavelengths of laser light as a mirror moves. Gravitational-wave detectors measure mirror motions smaller than a proton’s width this way. From a car’s spinning cable to ripples in spacetime, every speedometer is still v = d ÷ t underneath.
The Speed Calculator solves the speed triangle in SI-consistent units: v = d ÷ t, d = v × t, t = d ÷ v, converting mph (×1.60934) and m/s (×3.6) to km/h internally, and reporting time as decimal hours plus h/min. Key facts: results are average speed unless speed is constant; convert minutes to hours (÷60) before computing; speed is scalar while velocity adds direction.
Speed = distance ÷ time (v = d ÷ t). The same triangle gives distance = speed × time and time = distance ÷ speed.
Divide total distance by total time, including all stops: a 200 km trip taking 2.5 hours door-to-door averages 80 km/h.
Speed is how fast (scalar, e.g. 60 km/h). Velocity is how fast in which direction (vector, e.g. 60 km/h north). Changing direction changes velocity even at constant speed.
Multiply by 1.60934: 60 mph ≈ 96.6 km/h. To go the other way, divide by 1.60934.
Multiply by 3.6: 10 m/s = 36 km/h. Divide by 3.6 to convert back.
Because stops count. Time spent at red lights, in traffic, or parked is part of total time, dragging the average below your cruising speed.
Casual riders average 15–20 km/h, fit commuters 25–30 km/h, and racers 40+ km/h on flat roads.
t = d ÷ v = 100 ÷ 80 = 1.25 hours, which is 1 hour 15 minutes.
Cite this page as: Speed Calculator. Sigma Calculator. Retrieved October 11, 2026, from https://sigmacalculator.net/math-calculators/speed-calculator/
Last updated: October 11, 2026