Speed Distance Time Calculator

The distance formula

The relationship between speed, distance, and time is one of the most fundamental concepts in physics and everyday life.

Formulas

The three variables are related by these equations:

$$\text{Distance} = \text{Speed} \times \text{Time} math \text{Speed} = \frac{\text{Distance}}{\text{Time}} math \text{Time} = \frac{\text{Distance}}{\text{Speed}}$$

The SDT triangle

A helpful memory aid:

    D
   ───
  S × T

Cover the variable you want to find:

• Cover D: S × T (multiply)
• Cover S: D ÷ T (divide)
• Cover T: D ÷ S (divide)

Example calculations

Finding speed

A car travels 150 miles in 3 hours:

$$\text{Speed} = \frac{150 \text{ miles}}{3 \text{ hours}} = 50 \text{ mph}$$

Finding distance

Running at 6 mph for 45 minutes (0.75 hours):

$$\text{Distance} = 6 \text{ mph} \times 0.75 \text{ hours} = 4.5 \text{ miles}$$

Finding time

Driving 200 km at 80 km/h:

$$\text{Time} = \frac{200 \text{ km}}{80 \text{ km/h}} = 2.5 \text{ hours}$$

Unit conversions

Speed conversions

From	To	Multiply by
mph	km/h	1.609
km/h	mph	0.621
m/s	km/h	3.6
km/h	m/s	0.278

Time conversions

From	To	Factor
hours	minutes	× 60
minutes	seconds	× 60
hours	seconds	× 3600

Practical applications

Travel planning

Calculate arrival times and trip durations:

• 300-mile trip at 60 mph = 5 hours
• Add buffer time for stops, traffic, and breaks

Running and fitness

Track pace and performance:

• 5K (3.1 miles) in 25 minutes = 7.44 min/mile pace
• Marathon pace of 9 min/mile = 3:55 finish time

Aviation

Aircraft calculate ground speed considering wind:

• Airspeed + tailwind = higher ground speed
• Airspeed - headwind = lower ground speed

Shipping and logistics

Estimate delivery times and optimize routes based on distances and average speeds.

Average speed

For trips with varying speeds, use total distance divided by total time:

$$\text{Average Speed} = \frac{\text{Total Distance}}{\text{Total Time}}$$

Example: Drive 30 miles at 60 mph, then 30 miles at 30 mph

• Time 1: 30 ÷ 60 = 0.5 hours
• Time 2: 30 ÷ 30 = 1 hour
• Average: 60 miles ÷ 1.5 hours = 40 mph

The average is NOT simply (60 + 30) ÷ 2 = 45 mph!

Relative speed

When objects move toward each other, add their speeds. When moving in the same direction, subtract.

Two cars 100 miles apart:

• Driving toward each other at 50 mph each: 100 ÷ 100 = 1 hour to meet
• One chasing the other (50 mph vs 40 mph): 100 ÷ 10 = 10 hours to catch up

Common speed references

Activity	Typical Speed
Walking	3-4 mph
Jogging	5-6 mph
Cycling	12-18 mph
Highway driving	60-75 mph
Commercial aircraft	500-600 mph
Speed of sound	767 mph