Speed, Distance, Time Calculator
Speed, distance, time calculator with unit conversion. Solve for speed, distance or time using S = D/T, convert between km/h, m/s, mph and knots, and compute average speed for multi-leg trips.
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Speed, Distance, Time Calculator
Use this calculator to solve for speed, distance or time from the basic relationship \(v = d / t\). Mix units freely: kilometres, miles, metres, nautical miles, seconds, minutes or hours.
The tool also computes equivalent speeds in m/s, km/h, mph and knots, and includes an average speed calculator for multi-leg trips.
Solve for speed, distance or time
Examples: 5 km, 2000 m, 3 miles, 2.5 nautical miles.
Examples: 2 h, 45 min, 30 s. You can use decimals (e.g. 1.5 h).
Choose the units of the speed you know.
The result table will show all units; this setting controls the highlighted one.
Use dot or comma as decimal separator. Empty fields are treated as unknowns.
Average speed for multi-leg trips
Average speed over a whole journey is defined as \( \text{average speed} = \dfrac{\text{total distance}}{\text{total time}} \), not the simple average of segment speeds. Use this section to combine several legs.
| Leg | Distance | Unit | Time | Unit |
|---|
Tip: you can mix units across legs (e.g. some in km, some in miles). The calculator converts everything internally and reports the global average speed.
Speed–distance–time relationship
The core relationship between speed, distance and time is
\( v = \dfrac{d}{t}, \quad d = v \cdot t, \quad t = \dfrac{d}{v} \)
where \(v\) is speed, \(d\) is distance, and \(t\) is time.
As long as you know any two of the three quantities, you can compute the third. The only strict requirement is to keep units consistent – for example, kilometres with hours or metres with seconds.
Speed–distance–time triangle
A popular memory aid is the speed–distance–time triangle. Draw a triangle, put distance \(d\) at the top, and speed \(v\) and time \(t\) at the bottom corners:
d
v t
Cover the quantity you want: if you cover \(v\), the remaining layout shows \(d / t\); cover \(d\), you see \(v \cdot t\); cover \(t\), you see \(d / v\).
Worked examples
Example 1 – Find speed
A car travels 150 km in 2 hours. What is its average speed?
\( v = \dfrac{d}{t} = \dfrac{150 \text{ km}}{2 \text{ h}} = 75 \text{ km/h}. \)
Example 2 – Find distance
A runner maintains a speed of 12 km/h for 30 minutes. How far do they run?
Convert 30 minutes to hours: \( 30 \text{ min} = 0.5 \text{ h} \). \( d = v \cdot t = 12 \text{ km/h} \times 0.5 \text{ h} = 6 \text{ km}. \)
Example 3 – Find time
A cyclist travels at 20 km/h and needs to cover 35 km. How long will it take?
\( t = \dfrac{d}{v} = \dfrac{35 \text{ km}}{20 \text{ km/h}} = 1.75 \text{ h} \approx 1 \text{ h } 45 \text{ min}. \)
Speed, distance, time – frequently asked questions
Formula (LaTeX) + variables + units
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\( v = \dfrac{d}{t}, \quad d = v \cdot t, \quad t = \dfrac{d}{v} \) where \(v\) is speed, \(d\) is distance, and \(t\) is time.
\( v = \dfrac{d}{t} = \dfrac{150 \text{ km}}{2 \text{ h}} = 75 \text{ km/h}. \)
Convert 30 minutes to hours: \( 30 \text{ min} = 0.5 \text{ h} \). \( d = v \cdot t = 12 \text{ km/h} \times 0.5 \text{ h} = 6 \text{ km}. \)
\( t = \dfrac{d}{v} = \dfrac{35 \text{ km}}{20 \text{ km/h}} = 1.75 \text{ h} \approx 1 \text{ h } 45 \text{ min}. \)
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Last code update: 2026-01-19
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