Solve for speed, distance, or time from any two values. Supports km/h, mph, m/s, knots, with travel time comparisons and fuel cost estimates.
A flexible physics and travel calculator that solves the classic speed = distance ÷ time equation in any direction. Pick the unknown, enter the other two values in your preferred units (metric, imperial, SI, or nautical), and get instant results auto-converted to every supported unit. See how long common distances take at your speed (100m, 1km, 10km, marathon, around the world), compare your speed against walking, running, cycling, highway driving, commercial flight, and the speed of sound, and optionally estimate fuel cost for a road trip.
Every motion problem in everyday life and introductory physics reduces to one equation: speed equals distance divided by time. Cover any one of the three with your finger and the remaining two tell you the formula — distance over time gives speed, speed times time gives distance, distance over speed gives time. This calculator lets you skip the algebra and the unit-conversion errors.
A speed of 60 has no meaning without a unit: 60 km/h is a city street, 60 mph is a highway, 60 m/s is a hurricane, and 60 knots is a fast boat. Mixing units is one of the most common sources of error — NASA famously lost a Mars probe in 1999 because one team used pounds-force and another used newtons. The calculator normalises everything to SI base units (meters, seconds, m/s) before solving.
The travel-time and speed-comparison panels turn raw numbers into intuition. Seeing that a 10 km commute at 30 km/h takes 20 minutes — but only 6 minutes at 100 km/h — makes traffic costs concrete. Comparing your speed to walking (5 km/h), commercial flight (900 km/h), or the speed of sound (1235 km/h) gives a sense of scale that bare numbers cannot.
The three rearrangements of one equation: Speed = Distance ÷ Time, Distance = Speed × Time, Time = Distance ÷ Speed. All inputs are normalised to SI units (meters, seconds, m/s) internally so any combination of units works correctly.
It calculates average speed — total distance divided by total time. Instantaneous speed is the value at a specific moment (what a speedometer shows) and requires calculus or sensor data. For travel planning, average speed is what you want.
We use exact international definitions: 1 mile = 1609.344 m, 1 nautical mile = 1852 m, 1 knot = 1 nmi/h, 1 mph = 0.44704 m/s. Results are rounded for readability but computed at full double precision.
Use m/s for physics problems, scientific work, and SI-based calculations — it pairs cleanly with acceleration in m/s². Use km/h or mph for everyday travel and vehicle speeds. Knots are standard in aviation and marine navigation.
It is a flat projection: distance × economy × price. Real fuel use depends on speed (efficiency drops above ~90 km/h), terrain, A/C, traffic, load, and driving style. Treat it as a baseline and add ~10-20% for highway trips with hills.
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