Direct answer
In symbolic form:
In this formula, km represents kilometers and mi represents miles.
Use the Miles to Kilometers Converter to calculate another distance.
Why the formula uses 1.609344
One international mile contains exactly 5,280 international feet. One international foot equals exactly 0.3048 meter.
5,280 x 0.3048 = 1,609.344 meters
1,609.344 / 1,000 = 1.609344 kilometers
1 mile = exactly 1.609344 kilometersBecause the mile and foot have defined metric relationships, the factor 1.609344 is exact.
Apply the formula step by step
- Start with the distance in miles.
- Multiply the mile value by 1.609344.
- Keep the complete calculation result.
- Round the final kilometer value when appropriate.
- Write the unit as km or kilometers.
Formula example: 1 mile
km = mi x 1.609344
km = 1 x 1.609344
km = 1.609344
1 mile = 1.609344 kilometersFormula example: 5 miles
km = 5 x 1.609344
km = 8.04672
5 miles = 8.04672 kilometersFormula example: 50 miles
km = 50 x 1.609344
km = 80.4672
50 miles = 80.4672 kilometersFormula example: 100 miles
km = 100 x 1.609344
km = 160.9344
100 miles = 160.9344 kilometersUsing the formula with decimal miles
Example: 2.5 miles
km = 2.5 x 1.609344
km = 4.02336
2.5 miles = 4.02336 kilometersExample: 3.1 miles
km = 3.1 x 1.609344
km = 4.9889664
3.1 miles = 4.9889664 kilometersExample: 13.1 miles
km = 13.1 x 1.609344
km = 21.0824064
13.1 miles is approximately 21.08241 kilometersUsing the formula with fractional miles
Example: half a mile
1 / 2 = 0.5 mile
km = 0.5 x 1.609344
km = 0.804672
1/2 mile = 0.804672 kilometerExample: 2 1/4 miles
2 1/4 miles = 2.25 miles
km = 2.25 x 1.609344
km = 3.621024
2 1/4 miles = 3.621024 kilometersReverse kilometers-to-miles formula
To reverse the conversion, divide kilometers by 1.609344.
Open the Kilometers to Miles Converter for the reverse calculation.
Formula reference table
| Miles | Calculation | Kilometers |
|---|---|---|
| 1 mi | 1 x 1.609344 | 1.609344 km |
| 5 mi | 5 x 1.609344 | 8.04672 km |
| 10 mi | 10 x 1.609344 | 16.09344 km |
| 25 mi | 25 x 1.609344 | 40.2336 km |
| 50 mi | 50 x 1.609344 | 80.4672 km |
| 100 mi | 100 x 1.609344 | 160.9344 km |
Exact factor versus shortened factors
| Factor | Typical use | Precision |
|---|---|---|
| 1.609344 | Exact conversion | Exact factor |
| 1.609 | Shortened calculation | Close approximation |
| 1.61 | General comparison | Rounded approximation |
| 1.6 | Mental calculation | Quick estimate |
How rounding affects the formula result
13.1 x 1.609344 = 21.0824064 kilometers
Rounded to four decimals: 21.0824 kilometers
Rounded to three decimals: 21.082 kilometers
Rounded to two decimals: 21.08 kilometers
Rounded to one decimal: 21.1 kilometers
The rounding level should reflect the accuracy of the original mile distance.
Statute miles and nautical miles
The factor 1.609344 applies to the international statute mile, commonly used for road and land distances.
A nautical mile is a different unit and equals exactly 1.852 kilometers. Do not use the statute-mile formula for nautical distances.
Formula mistakes to avoid
Dividing miles by 1.609344
Division converts in the reverse direction from kilometers to miles.
Using 1.6 as an exact factor
The factor 1.6 is useful only for estimation.
Confusing statute miles and nautical miles
These units have different metric lengths.
Rounding the input before conversion
Preserve the complete original mile value.
Related miles-to-kilometers guides
Reverse the conversion
Use the Kilometers to Miles Converter to convert a kilometer distance back into miles.
Frequently asked questions
What is the formula for converting miles to kilometers?
Multiply miles by exactly 1.609344.
Is 1.609344 an exact conversion factor?
Yes. One international statute mile equals exactly 1.609344 kilometers.
Can the formula be used with decimal miles?
Yes. Multiply the complete decimal-mile value by 1.609344.
What is the reverse formula?
Divide kilometers by 1.609344 to calculate miles.