Whether you're planning a road trip, training for a marathon, or helping children with GCSE maths, understanding the relationship between speed, distance, and time is essential. This guide covers the formulas, provides practical examples, and includes UK-specific journey planning information.
The Three Core Formulas
Speed, distance, and time are related by three simple formulas. If you know any two values, you can calculate the third:
Distance = Speed × Time
Time = Distance ÷ Speed
• Cover D → S × T (Speed × Time)
• Cover S → D ÷ T (Distance ÷ Time)
• Cover T → D ÷ S (Distance ÷ Speed)
Try Our Free Speed Distance Time Calculator
Get instant results with our Speed Distance Time Calculator. Also check our Running Pace Calculator and Miles to KM Converter.
Practical Examples
Example 1: Finding Time
Solution: Time = Distance ÷ Speed
Time = 180 ÷ 60 = 3 hours
Example 2: Finding Distance
Solution: Distance = Speed × Time
Distance = 50 × 2.5 = 125 miles
Example 3: Finding Speed
Solution: Speed = Distance ÷ Time
Speed = 90 ÷ 1.5 = 60 mph
UK Speed Limits
Understanding UK speed limits helps plan realistic journey times:
| Road Type | Cars | Towing/Caravans | Goods Vehicles |
|---|---|---|---|
| Motorways | 70 mph | 60 mph | 60 mph (70 if ≤7.5t) |
| Dual carriageways | 70 mph | 60 mph | 60 mph |
| Single carriageway | 60 mph | 50 mph | 50 mph |
| Built-up areas | 30 mph | 30 mph | 30 mph |
| 20 mph zones | 20 mph | 20 mph | 20 mph |
Journey Time Reference Tables
Time by Distance and Speed
| Distance | @ 30 mph | @ 50 mph | @ 60 mph | @ 70 mph |
|---|---|---|---|---|
| 10 miles | 20 min | 12 min | 10 min | 9 min |
| 25 miles | 50 min | 30 min | 25 min | 21 min |
| 50 miles | 1h 40m | 60 min | 50 min | 43 min |
| 75 miles | 2h 30m | 90 min | 1h 15m | 64 min |
| 100 miles | 3h 20m | 2 hours | 1h 40m | 1h 26m |
| 150 miles | 5 hours | 3 hours | 2h 30m | 2h 9m |
| 200 miles | 6h 40m | 4 hours | 3h 20m | 2h 51m |
Common UK Journey Distances
| Route | Distance | Realistic Time* |
|---|---|---|
| London to Birmingham | 120 miles | 2-2.5 hours |
| London to Manchester | 200 miles | 3.5-4 hours |
| London to Edinburgh | 400 miles | 7-8 hours |
| Birmingham to Leeds | 115 miles | 2-2.5 hours |
| Manchester to Glasgow | 220 miles | 3.5-4 hours |
| Bristol to Cardiff | 45 miles | 50-70 min |
| Edinburgh to Glasgow | 47 miles | 1-1.5 hours |
*Including traffic and rest stops
• Motorway-dominant: 55-60 mph average
• Mixed roads: 40-45 mph average
• Urban/A-road: 30-35 mph average
• Add 15-30 minutes per 2 hours for rest stops
• Add 30% extra time for rush hour travel
Speed Conversions
| MPH | KPH | m/s | Feet/second |
|---|---|---|---|
| 20 mph | 32 kph | 8.9 m/s | 29.3 ft/s |
| 30 mph | 48 kph | 13.4 m/s | 44 ft/s |
| 40 mph | 64 kph | 17.9 m/s | 58.7 ft/s |
| 50 mph | 80 kph | 22.4 m/s | 73.3 ft/s |
| 60 mph | 97 kph | 26.8 m/s | 88 ft/s |
| 70 mph | 113 kph | 31.3 m/s | 102.7 ft/s |
| 100 mph | 161 kph | 44.7 m/s | 146.7 ft/s |
Running and Walking Calculations
The formulas work for any form of travel:
| Activity | Typical Speed | Time per Mile | Time per 5K |
|---|---|---|---|
| Walking (leisurely) | 3 mph | 20 minutes | 62 minutes |
| Walking (brisk) | 4 mph | 15 minutes | 47 minutes |
| Jogging | 5 mph | 12 minutes | 37 minutes |
| Running (recreational) | 6 mph | 10 minutes | 31 minutes |
| Running (fast) | 8 mph | 7.5 minutes | 23 minutes |
| Elite marathon pace | 13 mph | 4.6 minutes | 14 minutes |
Speed (mph) = 60 ÷ Pace (minutes per mile)
Example: 10-minute miles = 60 ÷ 10 = 6 mph
Working with Time Formats
Time calculations often need conversion between formats:
| Decimal Hours | Hours:Minutes | Total Minutes |
|---|---|---|
| 0.25 | 0:15 | 15 |
| 0.5 | 0:30 | 30 |
| 0.75 | 0:45 | 45 |
| 1.0 | 1:00 | 60 |
| 1.25 | 1:15 | 75 |
| 1.5 | 1:30 | 90 |
| 1.75 | 1:45 | 105 |
| 2.0 | 2:00 | 120 |
• Decimal to minutes: Multiply decimal part by 60 (e.g., 0.75 × 60 = 45 minutes)
• Minutes to decimal: Divide minutes by 60 (e.g., 45 ÷ 60 = 0.75 hours)
Understanding the Speed-Distance-Time Relationship
The speed-distance-time triangle is one of the most fundamental relationships in physics and everyday navigation. The three formulas are interconnected: Speed = Distance / Time, Distance = Speed x Time, and Time = Distance / Speed. Understanding any two of these values allows you to calculate the third. These calculations underpin everything from satellite navigation systems to marathon pacing strategies and are taught in the UK national curriculum at Key Stage 3.
When working with these formulas, consistency of units is critical. If speed is in miles per hour and distance is in miles, the resulting time will be in hours. Mixing units produces meaningless results. In the UK, road distances and speed limits use miles and miles per hour, but scientific and athletics contexts use metres and kilometres, requiring conversion between systems. Average speed differs from instantaneous speed, which is important for understanding average speed camera zones on UK motorways.
A journey of 60 miles completed in 1 hour and 30 minutes has an average speed of 40 mph, but the actual speed at any given moment may have varied between 0 mph in traffic and 70 mph on the motorway. Average speed cameras calculate the time between two fixed points and determine whether your average speed exceeded the limit, regardless of how your actual speed varied during that section.
• 30 mph: 23 metres (75 feet) total stopping distance
• 50 mph: 53 metres (175 feet) total stopping distance
• 70 mph: 96 metres (315 feet) total stopping distance
These figures assume dry conditions and an alert driver. In wet conditions, braking distances at least double.
Practical UK Applications
At 70 mph on a UK motorway, you cover approximately 1.17 miles per minute, meaning a 200-mile journey takes approximately 2 hours 51 minutes of pure driving time, to which you should add time for fuel stops, traffic, and rest breaks. The Highway Code recommends a 15-minute break at least every 2 hours. For UK runners, pace calculations use minutes per mile or minutes per kilometre. A Parkrun 5K at 6 minutes per kilometre gives a finish time of 30 minutes.
UK rail journey planning often involves comparing speed and time of different routes. A direct London-to-Edinburgh LNER train covers approximately 393 miles in 4 hours 20 minutes, averaging about 91 mph. The same journey by car takes 6 to 7 hours at an average of 57 to 67 mph including traffic. These comparisons help travellers choose the most time-efficient transport option for long-distance UK journeys.
Frequently Asked Questions
How do average speed cameras calculate my speed?
Average speed cameras record your number plate and exact time at two fixed points. The system divides the known distance by elapsed time to determine average speed. If the distance is 5 miles and you pass between cameras in 4 minutes, your average speed is 75 mph. Modern SPECS camera systems cover all lanes, so changing lanes does not defeat detection.
How do I calculate journey time for a UK road trip?
Divide total distance by expected average speed. For UK motorways, use 55 to 60 mph as a realistic average accounting for roadworks and junctions. For A-roads, use 35 to 45 mph. A 300-mile motorway journey at 57 mph takes approximately 5 hours 15 minutes of driving time, plus stops.
What speed units does the UK use?
The UK uses miles per hour (mph) for road speed limits and vehicle speedometers. However, athletics, cycling, and science use kilometres per hour (km/h) or metres per second (m/s). To convert mph to km/h, multiply by 1.609. To convert km/h to mph, multiply by 0.621. The UK is the only European country that uses miles rather than kilometres for road distances.
Speed Limits and Distance Calculations in the UK
The United Kingdom uses miles per hour (mph) for all road speed limits and vehicle speedometers, making it one of only a handful of countries worldwide that has not adopted kilometres per hour for road transport. UK speed limits are set out in the Road Traffic Regulation Act 1984 and vary by road type: 20 mph in many residential and urban areas (increasingly common since the introduction of blanket 20 mph zones in Wales in September 2023), 30 mph on roads with street lighting, 60 mph on single carriageways, and 70 mph on dual carriageways and motorways. Understanding speed-distance-time relationships helps drivers plan journeys, estimate arrival times, and understand how speed affects braking distances.
Journey time calculations are particularly relevant for UK commuters. According to the Office for National Statistics, the average commute in England is approximately 30 minutes each way. However, average speeds on UK roads vary dramatically: urban speeds average around 20 mph during peak hours, while motorway speeds average 60 to 65 mph under normal traffic conditions. The Department for Transport publishes annual road traffic statistics showing that total miles driven on UK roads exceed 325 billion per year. Using the speed-distance-time formula, a 15-mile urban commute at an average 20 mph takes 45 minutes, while the same distance on a clear motorway at 60 mph takes just 15 minutes.
Stopping distances are a critical application of speed-distance-time calculations tested in the UK driving theory exam. The Highway Code provides stopping distances that every learner driver must memorise: at 30 mph the overall stopping distance is 23 metres (75 feet), at 50 mph it is 53 metres (175 feet), and at 70 mph it is 96 metres (315 feet). These figures combine thinking distance and braking distance. In wet conditions, stopping distances at least double, and on icy roads they can increase tenfold. Speed cameras and average speed check zones on UK motorways use precisely these distance-time calculations to detect speeding offences.
Practical Tips for Speed-Distance-Time Calculations
- Use the triangle method: Draw a triangle with Distance at the top, Speed at the bottom left, and Time at the bottom right. Cover what you want to find: D = S x T, S = D / T, T = D / S.
- Convert units before calculating: Ensure speed and distance use compatible units. If your speed is in mph and distance in kilometres, convert one to match the other before applying the formula.
- Account for stops and delays: When estimating UK journey times, add 10 to 20 percent extra time for traffic lights, roundabouts, congestion, and fuel stops to get a more realistic arrival estimate.
More Questions About Speed, Distance and Time
Why does the UK use miles instead of kilometres for road distances?
How do average speed cameras work on UK motorways?
What speed-distance-time questions appear on the UK driving theory test?
Emma Thompson
Senior Content Editor
Emma is a senior content editor with a background in financial journalism. She specialises in making UK regulations and calculator tools understandable for consumers, working closely with qualified professionals to ensure accuracy.