Which units does this length converter use?
Millimeters, centimeters, meters, kilometers, inches, feet, yards, and miles only. Enter one value, one from-unit, and one to-unit. Weight, temperature, and cooking units are not used on this tool.
Length Converter
Convert one length into another across millimeters, centimeters, meters, kilometers, inches, feet, yards, and miles. Enter one value, one from-unit, and one to-unit. The page converts through exact millimeters in a single step, then rounds the display half-up to two decimals. One foot is 30.48 centimeters and 0.30 meters. This is an everyday length estimate only, not a survey or engineering measurement. Weight, temperature, and cooking units are not on this tool.
How length conversion works
Every length on this page is turned into millimeters with an exact factor, then into the unit you asked for. One inch is 25.4 millimeters. One foot is 304.8 millimeters. One yard is 914.4 millimeters. One mile is 1609344 millimeters. One centimeter is 10 millimeters, one meter is 1000 millimeters, and one kilometer is 1000000 millimeters.
The exact result is the value times the from-unit factor, divided by the to-unit factor. The page rounds that exact result half-up to two decimals. It does not round an intermediate unit and then convert again. One foot is exactly 0.3048 meters, which displays as 0.30 meters. The same foot is exactly 30.48 centimeters. If you took the rounded 0.30 meters and converted that to centimeters you would get 30.00, which is not the direct result.
One mile is exactly 1609.344 meters, which is 1.609344 kilometers and displays as 1.61 kilometers, not 1.60. One hundred centimeters is 1.00 meter and 39.37 inches. Zero is allowed and displays as 0.00. Empty, non-numeric, and negative values are rejected. This tool does not convert weight, temperature, or cooking units.
Worked example
1 foot converts to 30.48 centimeters. The exact millimeter count is 304.8, and 304.8 ÷ 10 = 30.48. The same foot is exactly 0.3048 meters, which displays as 0.30 meters, not 0.31. This is an everyday length estimate only, not a survey or engineering measurement.
Formula
result = (value × millimeters per from-unit) / millimeters per to-unit. Display = round2(exact result), half-up to 2 decimals. Do not chain a rounded intermediate. 1 in = 25.4 mm, 1 ft = 304.8 mm, 1 yd = 914.4 mm, 1 mi = 1609344 mm, 1 cm = 10 mm, 1 m = 1000 mm, 1 km = 1000000 mm, 1 mm = 1 mm. round2 is the same helper as gpa/concrete round2 and discount roundMoney.
- v
- The length you enter. Zero is allowed. Empty, non-numeric, and negative values are rejected.
- mm_from
- Exact millimeters in one from-unit. Feet are the literal 304.8, not a rounded chain of inches.
- mm_to
- Exact millimeters in one to-unit. The division uses this factor directly.
- round2
- Half-up to 2 decimals, applied once to the exact result. Not banker's rounding.
Disclaimer
An everyday length estimate only, not a survey or engineering measurement. This page converts millimeters, centimeters, meters, kilometers, inches, feet, yards, and miles through exact millimeter factors and rounds the display half-up to two decimals. It does not convert weight, temperature, or cooking units.
Frequently asked questions
Why is 1 foot both 30.48 centimeters and 0.30 meters?
One foot is 304.8 millimeters. Divided by 10 that is exactly 30.48 centimeters. Divided by 1000 that is exactly 0.3048 meters, which rounds half-up to two decimals as 0.30, not 0.31. The page does not convert the rounded 0.30 meters onward. That chained step would show 30.00 centimeters, which is not the direct result.
Why does 1 mile show 1.61 kilometers?
One mile is 1609344 millimeters, which is exactly 1609.344 meters and exactly 1.609344 kilometers. Half-up to two decimals is 1.61, not 1.60. The page divides the exact millimeter count by 1000000. It does not round the meters to 1609.34 and then divide that rounded figure.
What is 100 centimeters in meters and inches?
100 centimeters is 1000 millimeters, which is exactly 1 meter and displays as 1.00 meter. The same 1000 millimeters divided by 25.4 is about 39.37008 inches, which displays as 39.37 inches.
What is 1 inch in centimeters?
One inch is 25.4 millimeters. Divided by 10 that is exactly 2.54 centimeters, which displays as 2.54.
Can I enter zero or a negative length?
Zero is allowed. Zero of any length unit displays as 0.00. A negative value is rejected. An empty value and a non-numeric value are rejected too.
Is this a survey measurement?
No. This is an everyday length estimate only, not a survey or engineering measurement. It uses the exact millimeter factors on this page and rounds the display to two decimals.