Open menu

Construction Unit Converter

Enter a length in metres or feet to see it as feet and inches to the nearest 1/16 in, decimal inches and feet, metres and millimetres. Enter a slope in percent to see the angle in degrees, the pitch as x:12 and the gradient as 1 in n. A 2% slope is 1.15°, 0.24:12 or 1 in 50.

Measurements

Units

Enter in metres or feet; see it in every unit.

Rise ÷ run × 100.

Results

Feet and inches (nearest 1/16)

8′ 3″

Millimetres

2,514.6 mm

Slope angle

1.15 °

Metres
2.5146 m
Inches
99 in
Feet
8.25 ft
Pitch (x:12)
0.24:12
Gradient (1 in n)
1:50
Show the working
  1. Length conversion1 in = 25.4 mm; 1 ft = 0.3048 m → 2.5146 m = 99 in
  2. Slope conversionatan(2 ÷ 100) = 1.15°; 2% × 12 = 0.24:12
Paper and orientation
Open the list

How to use the unit converter

  1. Choose Metric or Imperial for entering the length.
  2. Enter the length. All conversions update immediately.
  3. Enter the slope as a percentage (rise ÷ run × 100).

How the conversions work

Lengths use the exact international definitions: 1 in = 25.4 mm and 1 ft = 0.3048 m. Feet and inches are rounded to the nearest 1/16 in and simplified (8/16 becomes 1/2). For slopes, the angle is atan(percent ÷ 100), the pitch is percent × 12 ÷ 100, and the gradient is 100 ÷ percent.

Worked examples

Tape measure check. 2.5 m = 8′ 2 7/16″ = 98.425 in.

Drainage fall. A 2% fall is 1.15°, about ¼ in per foot (0.24:12), or 1 in 50.

Roof pitch. A 50% slope is 26.57° and a 6:12 pitch.

How to interpret the results

Use the fraction for marking out with an imperial tape, and the millimetre value for metric drawings. For slopes, use whichever form your drawings or code use.

Tips and common mistakes

  • Don’t round twice. Convert from the original measurement, not from an already rounded value.
  • Percent isn’t degrees. A 10% slope is only 5.7°.
  • Check which pitch convention your drawings use: x:12, degrees or percent.

Common conversions on site

Some conversions come up again and again. A 2.4 m stud is 7′ 10 1/2″, a 600 mm spacing is 23 5/8″, and a 16 in spacing is 406.4 mm. Common drainage falls of 1 in 40, 1 in 60 and 1 in 80 are 2.5%, 1.67% and 1.25%. A 4:12 roof pitch is 33.3% or 18.4°, and a 12:12 pitch is 100% or 45°. Use the converter for anything in between, and keep the original measurement on your drawings so rounding never builds up.

Fractions and accuracy

Imperial tapes are usually marked in sixteenths of an inch, so the converter rounds to the nearest 1/16 in, which is about 1.6 mm. For joinery and cabinet work that needs more precision, use the decimal inches or millimetres instead.

The roof pitch calculator goes further with rafter lengths and roof area, and the stair calculator works out risers and treads from a total rise in either unit system.

Assumptions and limitations

Fractions are rounded to 1/16 in; for finer work, use the decimal inches.

Frequently asked questions

How do I convert millimetres to feet and inches?

Divide millimetres by 25.4 to get inches, then divide by 12 for feet; the remainder is inches. The converter rounds to the nearest 1/16 in.

How do I convert percent slope to degrees?

Degrees = arctangent(percent ÷ 100). A 100% slope is 45°; a 2% slope is about 1.15°.

What is a 1 in 50 gradient?

A rise of 1 unit for every 50 units of run, which is a 2% slope.

What is x:12 pitch?

Rise in inches for every 12 inches of run, common for roofs in North America. Percent × 12 ÷ 100 gives the x.

Are the conversions exact?

Yes. 1 in is exactly 25.4 mm and 1 ft is exactly 0.3048 m by definition.

How do I convert a slope to a drop over a distance?

Multiply the run by the percent and divide by 100. A 2% fall over 5 m drops 100 mm.

Sources