Speed Distance Time Calculator
Calculate speed, distance or time from any two values. Free calculator with mph, km/h, miles, km conversions and UK speed limit reference. Updated 2026.
Last updated: February 2026
Speed Distance Time Calculator
Calculate any one of speed, distance or time given the other two values. Supports mph, km/h, m/s and more.
About This Calculator
This calculator is part of UK Calculator's comprehensive suite of financial, health, and utility tools designed specifically for UK residents. Use it for journey planning, school homework, physics problems, and more.
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- Accurate: Precise mathematical calculations with unit conversions
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Complete Guide to Speed, Distance and Time Calculations
The relationship between speed, distance and time is one of the most fundamental concepts in physics and everyday life. Whether you are planning a road trip, helping your child with GCSE maths homework, calculating running pace, or simply wondering how long your commute will take at different speeds, this guide covers everything you need to know about the speed-distance-time triangle.
The three formulas are interconnected: Speed = Distance ÷ Time, Distance = Speed × Time, and Time = Distance ÷ Speed. An easy way to remember is the SDT triangle — cover the variable you want to find, and the remaining two show you the formula. For example, cover "S" (speed) and you see D over T, meaning Distance divided by Time.
UK Speed Limits Reference
Speed limits in the UK are set in miles per hour (mph). Here is a complete reference for all vehicle types and road types:
| Road Type | Cars & Motorcycles | Vans & Car-Derived Vans | Goods Vehicles (>7.5t) |
|---|---|---|---|
| Built-up areas | 30 mph | 30 mph | 30 mph |
| Single carriageway | 60 mph | 50 mph | 40 mph |
| Dual carriageway | 70 mph | 60 mph | 50 mph |
| Motorway | 70 mph | 60 mph | 60 mph |
Wales 20 mph: Since September 2023, the default speed limit in residential areas in Wales changed from 30 mph to 20 mph. This applies to restricted roads with street lighting unless signposted otherwise. Always check local signage.
Worked Examples
Example 1: Finding Speed
You drive from London to Birmingham (120 miles) and the journey takes 2 hours 15 minutes.
Speed = Distance ÷ Time
= 120 ÷ 2.25 = 53.3 mph
Example 2: Finding Distance
You drive on the motorway at an average speed of 65 mph for 1 hour 40 minutes.
Distance = Speed × Time
= 65 × 1.667 = 108.3 miles
Example 3: Finding Time
You need to travel 45 miles to the airport. You expect an average speed of 30 mph due to traffic.
Time = Distance ÷ Speed
= 45 ÷ 30 = 1.5 hours (1 hour 30 minutes)
Speed Unit Conversion Reference
| mph | km/h | m/s | knots | UK Context |
|---|---|---|---|---|
| 20 | 32.2 | 8.9 | 17.4 | Wales residential / school zones |
| 30 | 48.3 | 13.4 | 26.1 | Built-up areas (England default) |
| 40 | 64.4 | 17.9 | 34.8 | Common suburban limit |
| 50 | 80.5 | 22.4 | 43.4 | Motorway roadworks |
| 60 | 96.6 | 26.8 | 52.1 | Single carriageway national limit |
| 70 | 112.7 | 31.3 | 60.8 | Motorway / dual carriageway limit |
📚 Read Our Comprehensive Guide
Learn more tips, tricks, and detailed explanations to get the most out of this calculator.
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Expert Reviewed — This calculator uses verified mathematical formulas. UK speed limits updated February 2026.
Last updated: February 2026 | UK speed limits verified
People Also Ask
Real-World UK Speed and Distance Applications
Understanding speed, distance, and time relationships is essential for everyday life in the UK, from planning car journeys to training for a marathon. Here are practical scenarios where these calculations matter most.
UK Road Journey Planning
UK motorway speed limits are 70 mph for cars, but average speeds are typically lower. According to Department for Transport data, the average speed on English motorways is around 59 mph due to congestion, roadworks, and variable speed limits managed by Highways England's smart motorway network. When planning a journey, using an average of 50-55 mph gives a more realistic estimate. For example, a 200-mile journey from London to Manchester takes roughly 3 hours 40 minutes at realistic motorway speeds, not the 2 hours 50 minutes that 70 mph would suggest.
Running and Cycling Pace Calculations
The UK has a thriving parkrun community with over 700 events every Saturday, and pace calculation is fundamental for runners. A typical 5K parkrun time of 25 minutes equates to a pace of 5 minutes per kilometre (or about 8 minutes per mile). For the London Marathon, the average finishing time is around 4 hours 30 minutes for the 26.2-mile course, which works out to approximately 10:18 per mile. Cyclists on UK roads average 12-15 mph in urban areas and 15-20 mph on country lanes, making a 50-mile sportive ride take between 2.5 and 4 hours depending on terrain and fitness.
Speed Camera Awareness
Average speed cameras (SPECS and VECTOR) are increasingly common across UK motorways and A-roads. These systems calculate your average speed between two fixed points using the formula: average speed = distance between cameras / time taken. Understanding this helps you maintain a consistent legal speed. For instance, if average speed cameras are 2 miles apart in a 50 mph zone, you need to take at least 2 minutes 24 seconds to travel between them. The National Police Chiefs' Council guidelines suggest enforcement typically begins at the speed limit plus 10% plus 2 mph, so 57 mph in a 50 zone, but this is discretionary and you should always aim to stay within the limit.