What formats can I type?

Feet with a foot mark, then inches and a fraction: 12'-6 1/2", 12' 6 1/2", 12' 6.5" or 12'. Inches on their own need an inch mark: 150.5" or 1/2".

How precise are the answers?

To the nearest 1/16 in. Fractions are reduced, so 8/16 shows as 1/2 and 4/16 as 1/4.

How do I convert feet and inches to decimal feet?

Divide the total inches by 12. 20'-4 1/4" is 244.25 in, and 244.25 / 12 = 20.354 ft. The calculator shows decimal feet under every answer.

Multiply covers repeats and scaling, including fractions: multiply by 0.5 to halve a dimension.

Free calculator

Feet and inches calculator

Turn each dimension into inches, do the sum, then turn it back into feet and inches. 12'-6 1/2" + 7'-9 3/4" is 150.5 + 93.75 = 244.25 in, which is 20'-4 1/4".

Your job

Operation

Dimensions

First dimension

Second dimension

Feet with ', inches with ", fractions like 1/2 or 3/16.

The lengths to one scale, and the answer to the nearest 1/16 in.

Answer

20.354ft

20'-4 1/4" to the nearest 1/16 in

Decimal feet

20.354ft

Total inches

244.2500in

The working, with your numbers

1. First in inches12'-6 1/2"= 150.5000 in
2. Second in inches7'-9 3/4"= 93.7500 in
3. Add150.5000 + 93.7500= 244.2500 in
4. Back to feet244.2500 / 12= 20'-4 1/4"

Typed those measurements in by hand?MetreMate measures them straight off your PDF plans. Free to start.

The formula, in plain words

1Convert each dimension to inches: feet times 12, plus the inches, plus the fraction.
2Add, subtract or multiply the inch values.
3Feet = the whole number of times 12 goes into the answer; the remainder is inches.
4Round the leftover fraction to the nearest 1/16 in and reduce it (8/16 is 1/2).

Worked example

Add 12'-6 1/2" and 7'-9 3/4".

1.12'-6 1/2" = 12 x 12 + 6.5 = 150.5 in.
2.7'-9 3/4" = 7 x 12 + 9.75 = 93.75 in.
3.Sum: 150.5 + 93.75 = 244.25 in.
4.Feet: 244.25 / 12 = 20 ft, remainder 244.25 - 240 = 4.25 in.

Answer: 20'-4 1/4".

Measured this off a plan? Do it in MetreMate

Upload the PDF, set the scale and measure on screen. MetreMate gives you the square feet, linear feet and counts off the plan; then you apply the thickness, pitch, waste or sheet size here. Runs in your browser, free to start, no credit card.

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How to measure it

Type dimensions the way they appear on the plans: 12'-6 1/2", 12' 6.5" or just inches like 150.5".
Use the inch mark (") for inches-only values so they aren't read as feet.
To repeat a dimension (six bays at 12'-6"), pick multiply and enter the count.

Where the numbers come from

Every default in the calculator comes from a published source. We list the source next to it so you can check.

What	Value	Source
Inches in one foot (the foot is exactly 12 inches)	12 in per ft	Wikipedia, Foot (unit) (checked 2026-10-01)

Manufacturers named here are the source of the number, not a recommendation. Confirm quantities with your supplier.

Frequently asked questions

Stop typing measurements in by hand

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