In this calculation I will show you how to convert 2 feet, 3 inches, 5/16ths to millimetres.
Work out how many feet you have and multiply this number by 12 to convert it into inches. For instance here we have 2 feet, so this equals 24 inches (as there are 12 inches to a foot).
Work out how many inches you have and add this to the number you worked out in step 1. Here we have 3 inches, so the total inches equals 24 + 3 which equal 27.
Convert to millimetres by multiplying by 25.4. So if we have 27 inches, multiply it by 25.4 to equal 685.8 mm.
If you have sub inches then work out the number of sub inches you have in the form of a fraction of sixteenths i.e 1/16, 2/16 etc. Multiply the number at the beginning or top of the fraction by 1.5875. So if you have 5/16ths the calculation is 5 x 1.5875. This equals 7.9375 mm.
Add up everything, so from step 3 we have 685.8 and from step 4 we have 7.9375. Added together this makes 693.7375mm, or 69.374cm, 0.694m.