Mixed-Unit Calculator
Type any mixed-unit length on each side. Add, subtract, multiply, divide. Read the result in 6 formats.
How to use
Type any mixed-unit length into the two fields. The calculator parses fractions, prime marks (foot ′ and inch ″), decimals, and any combination of metric and imperial units. Pick an operator. Read the result in millimetres, centimetres, metres, decimal inches, decimal feet, carpenter ft-in fraction, and m-cm split.
- Acceptable input examples:
3 ft 7 1/2 in,3'-7 1/2",5 m 30 cm,1 yd 2 ft 6 in,5'7",1.5 km 250 m,2.75 ft. - Units recognized:
mm cm m km in ft yd mi(and their long forms:inch inches foot feet metre metresetc.). Both′ 'and″ "are accepted as foot and inch. - Pick the operator: + add, − subtract, × multiply A by the numeric value of B, ÷ divide A by the numeric value of B.
- For × and ÷, only the number is used — units on B are ignored. So "5 ft 3 in × 2.5" = "13 ft 1.5 in".
Reviewed 6 June 2026 · methodology cited
About this calculator
A mixed-unit length is a measurement expressed in more than one unit — "3 feet 7 1/2 inches" instead of "43.5 inches", or "5 metres 30 centimetres" instead of "5.3 metres". Construction and architecture use mixed units all the time: dimensions are called out on drawings as feet-and-inches, height clearances as inches, lumber as fractional inches, and metric dimensions usually as metres-and-centimetres for any length over a metre.
This calculator parses mixed-unit lengths in either system, lets you add and subtract them (the most common operation), or multiply and divide by a scalar. It outputs the result in seven formats simultaneously — including the carpenter ft-in fraction format that is hard to find in general-purpose calculators.
How the parser works
The parser normalizes the input first: prime marks (′ and ') become "ft", double prime marks (″ and ") become "in", hyphens between numbers and units ("3-7" in feet-inches notation) become spaces. Lowercase the rest.
Then it scans the string for repeating (number)(unit) pairs. The number can be an integer, decimal, simple fraction ("1/2"), or mixed number ("3 1/2"). The unit is matched against a table of accepted abbreviations and long forms. Each pair contributes (number × unit_factor_in_mm) to a running total.
The sum is in millimetres internally (chosen as the canonical base because it's a small unit that avoids floating-point drift for typical construction values). All outputs are computed from that millimetre total.
The ft-in fraction output rounds the inches portion to the nearest 1/16 inch (the smallest division on a standard tape measure) and simplifies the fraction. So 1104.9 mm = 43.500 inches = 3 ft 7 1/2 in.
Accepted input syntax
| You type | Means | Normalized |
|---|---|---|
3'-7 1/2" | Feet-inches, prime marks, fraction | 3 ft 7.5 in = 43.5 in = 1104.9 mm |
3 ft 7 1/2 in | Feet-inches, written units | Same as above |
5 m 30 cm | Metres + centimetres | 530 cm = 5.3 m = 5300 mm |
1 yd 2 ft 6 in | Yards + feet + inches | 1.5 yd = 4.5 ft = 1371.6 mm |
5'7" | Feet-inches compact | 5 ft 7 in = 67 in = 1701.8 mm |
2.75 ft | Decimal feet | 2.75 ft = 33 in = 838.2 mm |
1.5 km 250 m | Mixed kilometres + metres | 1750 m = 1,750,000 mm |
1 1/2 in | Mixed inches (1 + 1/2) | 1.5 in = 38.1 mm |
1/4 in | Simple fraction inches | 0.25 in = 6.35 mm |
12 in | Inches only | 12 in = 1 ft = 304.8 mm |
Common patterns
When typing US imperial measurements, the prime marks are interchangeable: <code>3'-7"</code> and <code>3 ft 7 in</code> parse identically. Hyphens, spaces, and dashes between feet and inches are all OK — the parser strips them. Fractions can be either simple (<code>1/2</code>) or mixed (<code>1 1/2</code>), with a space between the integer and the fraction in mixed form.
When typing metric, you do not need to repeat the unit on each component. <code>5 m 30 cm</code> works, and so does <code>1.5 km 250 m</code>. Decimal commas (European convention) are not yet supported — use a decimal point.
For multiplication and division, the second value is treated as a pure number — its units are ignored. So <code>10 ft × 2</code> = 20 ft, and <code>10 ft × 2 m</code> = 20 ft (the "m" is dropped). This matches how a carpenter would say it: "twice ten feet". To get the area or product of two lengths, you need a separate area calculation, not this calculator.
Frequently asked questions
Why is "5 ft 3 in × 2 m" giving the same result as "5 ft 3 in × 2"?
Because multiplication treats the second value as a scalar (pure number). The units on side B are stripped when the operator is × or ÷. So both give "10 ft 6 in". To multiply length × length and get an area, use an area calculator instead.
What if my input has a typo or unknown unit?
Unknown units are silently dropped — that part of the input contributes zero. So "3 ft 7 inchz" would parse as "3 ft" only (1066.8 mm). Check the "parsed as" readout to verify the calculator understood your input the way you meant it.
Why doesn't the calculator accept a decimal comma (5,5 m)?
The parser currently requires a decimal point ("5.5 m"), not a comma. European-convention support is planned. For now, use a decimal point even on a French-language page.
How precise is the ft-in fraction output?
The inches portion is rounded to the nearest 1/16 inch — the smallest division on a standard 16-foot tape measure. So 43.55 inches displays as 3 ft 7 9/16 in. For finer precision use the decimal inches readout, which shows three decimal places.
Can I subtract a larger value from a smaller value?
Yes — the result will be negative. So "5 cm − 10 cm" = "−5 cm". Most output formats handle negatives; the ft-in fraction reads as "−0 ft 1 15/16 in" for a small negative value.
Does this work on a phone keyboard without easy access to ′ and ″?
Yes — straight quotes work: <code>5' 3"</code> is recognized exactly as <code>5′ 3″</code>. You can also write out "ft" and "in" with spaces: <code>5 ft 3 in</code>. The parser is permissive — try several patterns if one is awkward to type on mobile.