Speed, Distance & Time Calculator
Calculate speed, distance or time from the other two. Miles and km with the SDT triangle formula.
By Konstantin Iakovlev · Founder, Calks.uk
Last updated: · Verified against HMRC and GOV.UK 2026/27 rates
Speed
60.0 mph
96.6 km/h
Distance
150.0 miles
241.4 km
Time
2h 30m
2.50 decimal hrs
Disclaimer
This calculator is provided for informational purposes only and should not be considered as financial or tax advice. All calculations are performed locally in your browser — no personal data is collected or sent to our servers. Rates and thresholds are sourced from HMRC and GOV.UK and are updated for the current tax year. Always verify results with HMRC or consult a qualified professional before making financial decisions.
How It Works
Speed, distance and time are related by the formula: Speed = Distance ÷ Time. Given any two of the three values, this calculator finds the third. It supports miles per hour (mph), kilometres per hour (km/h) and metres per second (m/s), converting between them automatically.
The calculator is useful for journey planning, running pace calculations and physics problems. For journeys with multiple legs at different speeds, it calculates the correct average speed (total distance ÷ total time), which is not the same as the arithmetic mean of the speeds.
The triangle: Speed = Distance ÷ Time. Three equations: Speed = Distance ÷ Time; Distance = Speed × Time; Time = Distance ÷ Speed. Units must match — mph + miles + hours, OR km/h + km + hours. Convert: 60 mph = 1 mile/min = 88 ft/sec = 26.8 m/s. 100 km/h = 27.78 m/s = 62.1 mph. Athletics 10km in 50 min = 12 km/h pace. Marathon 42.195km in 4 hours = 10.55 km/h.
UK speed limits 2026. 20 mph: default urban residential (Wales since 2023; growing in English boroughs). 30 mph: built-up areas. 40-50 mph: signposted A-roads. 60 mph: national speed limit single carriageway. 70 mph: dual carriageway and motorway. Highway Code stopping distances at 30 mph: 23m (75ft) total; 60 mph: 73m (240ft); 70 mph: 96m (315ft). Wet roads: double these distances. Reaction time component: 0.7s standard.
Realistic UK journey times. Urban driving average 12-20 mph (London 12 mph). Motorway: 60-65 mph realistic (traffic). Rural A-roads: 35-45 mph. London-Manchester (200 miles): 3.5 hours motorway + breaks. London-Edinburgh: 8 hours road / 4.5 hours train. Cycling: 12-15 mph town, 18-22 mph club road. Walking: 3 mph leisurely, 4 mph brisk. Running: 6 mph recreational (10 min/mile), 10 mph competitive (6 min/mile).
Speed conversions worldwide. 1 mph = 1.609 km/h. 1 m/s = 3.6 km/h = 2.237 mph. 1 knot (nautical mile/hour) = 1.852 km/h = 1.151 mph. Mach 1 (speed of sound at sea level) = 1,235 km/h = 767 mph. Speed of light: 299,792,458 m/s. Useful: 60 mph ≈ 100 km/h; commercial flight 500-600 mph; Concorde was 1,354 mph (Mach 2.04); ICE/TGV trains 200 mph; Earth's rotation at equator 1,037 mph.
Time-distance-speed in real life. Trains: time = distance ÷ avg speed (including stops). London-Manchester train avg 80 mph including stops = 200/80 = 2h 30min. Average pace running: divide time by distance. 50 min for 10 km = 5:00/km. UK Parkrun 5K average finishing time 28:30 = 5:42/km pace. Cycling power vs speed: 200 watts ≈ 30 km/h on flat road. Triangle works for ANY motion: car, person, projectile, planet.
Example: Driving 150 miles in 2 hours 30 minutes
- Distance: 150 miles
- Time: 2.5 hours
- Speed: 150 ÷ 2.5 = 60 mph
- 60 mph = 96.56 km/h = 26.82 m/s
Frequently Asked Questions
- The Speed = Distance / Time triangle.
- Three equations: Speed = Distance ÷ Time; Distance = Speed × Time; Time = Distance ÷ Speed. Units must match — if speed in mph then distance in miles, time in hours. Convert: 60 mph = 1 mile/min = 88 ft/sec = 26.8 m/s. 100 km/h = 27.78 m/s = 62.1 mph. Athletics: 10 km in 50 min = 12 km/h average pace; marathon (42.195 km) in 4 hours = 10.55 km/h.
- UK speed limits and stopping distances.
- UK speed limits: 20 mph (urban residential since 2023 default in Wales, growing in England); 30 mph (built-up); 40-50 mph (single carriageway A-roads, signposted); 60 mph (national speed limit single carriageway); 70 mph (dual carriageway and motorway). Highway Code stopping distances at 30 mph: 23m (75ft) total; 60 mph: 73m (240ft); 70 mph: 96m (315ft). Wet roads: double these. Reaction time component: 0.7s standard (used 2-second 'gap rule').
- Travel-time estimation for UK journeys.
- Realistic average speeds: urban driving 15-20 mph (London 12 mph average); motorway 60-65 mph (rare to average 70 with traffic); rural A-roads 35-45 mph. London-Manchester (200 miles): 3.5 hours motorway driving + breaks. London-Edinburgh: 8 hours road / 4.5 hours train. Cycling commute: 12-15 mph in town, 18-22 mph club road cyclist. Walking: 3 mph leisurely, 4 mph brisk. Running: 6 mph (10 min/mile) recreational, 10 mph (6 min/mile) competitive.
- Speed conversion — units used worldwide.
- 1 mph = 1.609 km/h. 1 m/s = 3.6 km/h = 2.237 mph. 1 knot (nautical mile/hour) = 1.852 km/h = 1.151 mph. Mach 1 (speed of sound at sea level) = 1,235 km/h = 767 mph. Speed of light: 299,792,458 m/s. Useful: 60 mph ≈ 100 km/h; commercial flight 500-600 mph (800-960 km/h); ICE/TGV trains 200 mph; Concorde was 1,354 mph (Mach 2.04). Earth's rotation at equator: 1,037 mph (1,670 km/h).