31 millimeters in inches

Conversion formula
How to convert 31 millimeters to inches?

We know (by definition) that: $1\mathrm{mm}\approx 0.039370079\mathrm{in}$

We can set up a proportion to solve for the number of inches.

Now, we cross multiply to solve for our unknown $x$:

Conclusion: 31 ⁢ mm ≈ 1.220472449 ⁢ in

Conversion in the opposite direction

The inverse of the conversion factor is that 1 inch is equal to 0.819354838709678 times 31 millimeters.

It can also be expressed as: 31 millimeters is equal to $\frac{1}{\mathrm{0.819354838709678}}$ inches.

Approximation

An approximate numerical result would be: thirty-one millimeters is about one point two one inches, or alternatively, a inch is about zero point eight two times thirty-one millimeters.