Solve for speed, distance, or time by entering any two known values. Switch between mph, km/h, m/s and multiple distance units. Instant results with full working shown.
✓Last verified: April 2026 · Standard physics formula
miles
Please enter the distance.
hrs
Please enter the time.
mph
Please enter the speed.
Result
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Speed
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mph
Distance
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miles
Time
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hours
Also In
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Sources & Methodology
✓Speed, distance, and time calculations use fundamental kinematic equations from classical mechanics, consistent with definitions in the NIST Guide to SI Units and standard physics curricula worldwide.
The National Institute of Standards and Technology's authoritative guide to SI units defines metre, second, and their derived units (m/s, km/h) used in this calculator's conversion factors.
The National Highway Traffic Safety Administration publishes speed-distance-time relationships for road safety research, confirming the standard formulas and unit conversions used here.
Authoritative curriculum reference confirming the Speed = Distance / Time formula and its algebraic rearrangements taught in US middle and high school mathematics.
Formulas: Speed = Distance / Time | Distance = Speed x Time | Time = Distance / Speed. All inputs are converted to SI base units (meters, seconds) internally, then converted back to the user's chosen display units. Unit conversions: 1 mile = 1609.344 m, 1 km = 1000 m, 1 knot = 0.514444 m/s, 1 ft = 0.3048 m.
⏱ Last reviewed: April 2026
Speed Distance Time Formula: How to Calculate Any Variable
The speed, distance, and time relationship is one of the most practical formulas in everyday mathematics. Whether you are planning a road trip, working out your running pace, estimating a flight arrival, or solving a physics problem, these three quantities are always connected by the same equation. You only ever need to know two of the three values to find the third.
The Three Formulas — Derived from One Relationship
Speed = Distance / Time Distance = Speed x Time Time = Distance / Speed
All three formulas come from the same relationship: D = S x T. Rearrange algebraically to isolate any variable.
Find Speed: Drive 240 miles in 4 hours → Speed = 240 / 4 = 60 mph Find Distance: Drive at 70 mph for 2.5 hours → Distance = 70 x 2.5 = 175 miles Find Time: Travel 300 km at 100 km/h → Time = 300 / 100 = 3 hours
Speed Unit Conversion Quick Reference
Speed
mph
km/h
m/s
Knots
30 mph
30.00
48.28
13.41
26.07
60 mph
60.00
96.56
26.82
52.14
100 km/h
62.14
100.00
27.78
53.99
120 km/h
74.56
120.00
33.33
64.79
10 m/s
22.37
36.00
10.00
19.44
Speed of sound
767.27
1234.80
343.00
667.01
Common Travel Time Calculations
For road trips, the most useful calculation is time = distance / speed. A 500-mile road trip at an average of 65 mph takes 500 / 65 = 7.69 hours, or 7 hours and 41 minutes of driving time. Always add stop time separately — the formula only accounts for time actually moving. A realistic rule of thumb is to add 15-20 minutes of stops for every 2 hours of driving.
For international travel where distances are in kilometers, the same formula applies. London to Edinburgh is approximately 660 km by road. At an average motorway speed of 110 km/h: time = 660 / 110 = 6 hours driving. Paris to Amsterdam is approximately 500 km: at 120 km/h = 4.17 hours = 4 hours 10 minutes.
Speed Distance Time for Running and Exercise
Runners typically measure pace (minutes per mile or per km) rather than speed. To convert speed to pace: Pace (min/mile) = 60 / Speed (mph). A 6 mph running speed = 60/6 = 10:00 per mile pace. A 10 km/h running speed = 60/10 = 6:00 per km pace. Marathon distance is 42.195 km or 26.219 miles. A 4-hour marathon finish equals an average speed of 42.195/4 = 10.55 km/h or 6.55 mph, corresponding to a 9:09 per mile pace.
💡 Unit mismatch warning: The most common mistake when using speed-distance-time formulas is mismatched units. If speed is in mph, distance must be in miles and time in hours. If speed is in km/h, distance must be in kilometers and time in hours. This calculator handles all conversions automatically — just select your preferred units and enter the raw numbers.
Frequently Asked Questions
The three related formulas are: Speed = Distance / Time, Distance = Speed x Time, and Time = Distance / Speed. All three come from the same relationship D = S x T. You only need two of the three values to calculate the third. Enter any two known values in this calculator to find the missing one instantly.
Speed = Distance / Time. Divide the distance by the time. Example: 240 km in 3 hours = 80 km/h. 10 miles in 15 minutes = 10 / (15/60) = 10 / 0.25 = 40 mph. Make sure time is in the same unit as the denominator of your speed unit (hours for mph or km/h, seconds for m/s).
Distance = Speed x Time. Multiply speed by time. Example: 65 mph for 2.5 hours = 162.5 miles. 100 km/h for 90 minutes (1.5 hours) = 150 km. Always convert time to hours when using mph or km/h. Convert time to seconds when using m/s.
Time = Distance / Speed. Divide the total distance by the speed. Example: 300 miles at 60 mph = 5 hours. 450 km at 90 km/h = 5 hours. To convert decimal hours to hours and minutes, multiply the decimal part by 60. Example: 5.67 hours = 5 hours and 0.67 x 60 = 40 minutes = 5 hours 40 minutes.
Time = 100 / 60 = 1.6667 hours = 1 hour and 40 minutes. At 65 mph: 100/65 = 1.538 hours = 1 hour 32 minutes. At 70 mph: 100/70 = 1.429 hours = 1 hour 26 minutes. At 55 mph: 100/55 = 1.818 hours = 1 hour 49 minutes. Each 5 mph increase saves roughly 6-8 minutes over 100 miles.
Multiply km/h by 0.621371 to get mph. Example: 100 km/h x 0.621371 = 62.14 mph. Quick approximation: divide km/h by 1.6. To convert mph to km/h, multiply by 1.60934. Example: 60 mph x 1.60934 = 96.56 km/h. The speed limit in most UK roads is 70 mph = 112.65 km/h.
Average speed = Total Distance / Total Time. Do not average the speeds. Example: drive 100 miles at 50 mph (2 hours) then return 100 miles at 100 mph (1 hour). Total distance = 200 miles. Total time = 3 hours. Average speed = 200/3 = 66.67 mph, not 75 mph. The faster leg covers the same distance in less time, so it contributes less to the average.
Multiply m/s by 3.6 to get km/h. Example: 10 m/s x 3.6 = 36 km/h. 28 m/s (sprint speed) = 100.8 km/h. To convert km/h to m/s, divide by 3.6. To convert m/s to mph, multiply by 2.23694. The speed of sound is 343 m/s = 1234.8 km/h = 767.3 mph.
Pace (min/mile) = 60 / Speed (mph). At 6 mph: 60/6 = 10:00 min/mile. At 8 mph: 60/8 = 7:30 min/mile. At 10 mph: 60/10 = 6:00 min/mile. Pace (min/km) = 60 / Speed (km/h). At 10 km/h: 60/10 = 6:00 min/km. At 12 km/h: 60/12 = 5:00 min/km.
Speed is scalar — it only has magnitude (how fast). Velocity is a vector — it has both magnitude and direction. 60 mph is a speed. 60 mph north is a velocity. For everyday travel calculations like road trips and commutes, speed is the relevant quantity since we measure total distance travelled regardless of direction changes.
Calculate pure driving time using Time = Distance / Speed, then add stop time separately. Example: 400 miles at 65 mph = 6.15 hours driving. Adding two 20-minute stops (40 minutes = 0.67 hours): total trip = 6.15 + 0.67 = 6.82 hours = 6 hours 49 minutes. This calculator gives pure travel time — add your planned rest stops to get total trip duration.