Conversion formula

The conversion factor from inches to millimeters is 25.4, which means that 1 inch is equal to 25.4 millimeters:

1 in = 25.4 mm

To convert 1 inch into millimeters we have to multiply 1 by the conversion factor in order to get the length amount from inches to millimeters. We can also form a simple proportion to calculate the result:

1 in → 25.4 mm

1 in → L_(mm)

Solve the above proportion to obtain the length L in millimeters:

L_(mm) = 1 in × 25.4 mm

L_(mm) = 25.4 mm

The final result is:

1 in → 25.4 mm

We conclude that 1 inch is equivalent to 25.4 millimeters:

1 inch = 25.4 millimeters

Alternative conversion

We can also convert by utilizing the inverse value of the conversion factor. In this case 1 millimeter is equal to 0.039370078740157 × 1 inch.

Another way is saying that 1 inch is equal to 1 ÷ 0.039370078740157 millimeters.

Approximate result

For practical purposes we can round our final result to an approximate numerical value. We can say that one inch is approximately twenty-five point four millimeters:

1 in ≅ 25.4 mm

An alternative is also that one millimeter is approximately zero point zero three nine times one inch.

Conversion table

inches to millimeters chart

For quick reference purposes, below is the conversion table you can use to convert from inches to millimeters