Length Unit Converter
Metres, millimetres, feet and inches — every unit shown at once.
Quick answer
With the default inputs: Value 1 · From unit Metre · To unit FootConverted value 3.2808 ft
Edit the inputs below to recalculate.Inputs
Result
Converted value
3.2808ft
| Metre | 1m |
| Millimetre | 1000.00mm |
| Centimetre | 100cm |
| Decimetre | 10dm |
| Kilometre | 0.001km |
| Inch | 39.3701in |
| Foot | 3.2808ft |
| Yard | 1.0936yd |
| Mile | 0.000621mi |
| Chinese chi | 3chi |
All factors are exact definitions — the inch has been 25.4 mm by international agreement since 1959. The chi is taken as exactly 1/3 m; local practice varies.
Reverse: known result, work out one input
Enter a target result; the other inputs stay fixed and this one is worked out.
Formula
| Metric | 1 m = 10 dm = 100 cm = 1000 mm, 1 km = 1000 m |
| Imperial | 1 ft = 12 in, 1 yd = 3 ft, 1 mile = 1760 yd |
| Metric to imperial | 1 in = 25.4 mm, 1 ft = 0.3048 m |
| Chinese units | 1 chi = 1/3 m ≈ 333.33 mm, 1 cun = 33.33 mm |
| General rule | target = source value × source factor ÷ target factor |
1 metre converts to 3.2808 ft, 39.3701 in or 1000 mm. A 3.5 m floor height is 11.4829 ft, and a 1220 × 2440 mm sheet is exactly 4 ft × 8 ft.
Length unit conversion factors
| Unit | Symbol | In metres | In millimetres | Typical use |
|---|---|---|---|---|
| Metre | m | 1 | 1000 | Drawings |
| Millimetre | mm | 0.001 | 1 | Bar size, slab depth |
| Centimetre | cm | 0.01 | 10 | Fit-out dimensions |
| Kilometre | km | 1000 | 1000000 | Road distance |
| Inch | in | 0.0254 | 25.4 | Pipe size, imperial drawings |
| Foot | ft | 0.3048 | 304.8 | 4×8 sheets |
| Yard | yd | 0.9144 | 914.4 | Earthwork, fabric |
| Mile | mi | 1609.344 | 1609344 | Highway distance |
| Chinese chi | chi | 0.3333 | 333.3 | Spoken fit-out quotes |
How to work it out
- Confirm the source unit first. The commonest trap on drawings is that dimensions default to millimetres, but structural and architectural drawings may differ, and title blocks state the unit — read it before reading dimensions.
- Within metric, everything is decimal: 1 m = 10 dm = 100 cm = 1000 mm, and 1 km = 1000 m. Errors here are rare.
- Metric to imperial uses exact definitions: 1 in = 25.4 mm and 1 ft = 0.3048 m, both exact by definition rather than approximation. From these two every imperial length follows.
- Within imperial: 1 ft = 12 in, 1 yd = 3 ft, 1 mile = 1760 yd. Note that a mile is not a round number of feet — 5280 ft is a consequence, not the definition.
- Chinese municipal chi: 1 chi = 1/3 m ≈ 333.33 mm, 1 cun = 33.33 mm, 10 cun to the chi. Old drawings and legacy material lists use chi, and it is not the foot.
- Sanity-check the result. Three metres should come out near 9.8 ft; an answer of 0.9 or 98 means the source unit was wrong.
Where it goes wrong
- Treating a Chinese chi as a foot. The chi is 333 mm against the foot at 305 mm, so a 10-chi beam is 3.33 m, not 3.05 m — 28 cm apart.
- Confusing nominal pipe sizes with inches. A 4-fen pipe is half an inch (DN15), not four inches; a 1-cun pipe is DN25. These trade names are not decimal relationships.
- Using 25 mm instead of 25.4 mm for inches. The error is negligible on short lengths, but 100 inches becomes 2500 mm instead of 2540 — enough that steelwork will not fit.
- Multiplying or dividing by 1000 without checking the drawing unit. Architectural drawings are usually in millimetres, site and road layouts in metres, and BIM models may use metres. One mix-up is a factor of 1000.
Material and cost
The cost scales with member length. At fit-out stage 10 mm is an ugly joint; in steelwork 40 mm means a member is scrapped and remade at 5000-8000 CNY per tonne; in curtain walling 5 mm means retooling at tens of thousands per die set.
On site
- Fen and cun are pipe trade names: 4 fen = DN15, 6 fen = DN20, 1 cun = DN25, 1.2 cun = DN32, 1.5 cun = DN40, 2 cun = DN50. Memorising this beats looking it up.
- Section designations are in millimetres: L50×5 is a 50 mm leg at 5 mm thick, and a φ48×3.5 tube is 48 mm outside diameter at 3.5 mm wall. Not centimetres.
- Imported equipment and drawings are often in inches. Convert to millimetres for local fabrication, but keep 0.1 mm precision on mating faces — never round to whole millimetres there.
- A converter app is more reliable than remembered factors, but the error almost always lies in selecting the wrong source unit rather than in the arithmetic.
Basis
- GB/T 3100-3102 Quantities and units series
- GB 50001-2017 Uniform standard for building drawings, sheet sizes and drawing arrangement
- GB/T 50104-2010 Standard for architectural drawings
FAQ
Why can't inches and feet be handled as decimals?
Imperial is duodecimal: 1 ft = 12 in, 1 yd = 3 ft, 1 mile = 1760 yd. The commonest mistake on imperial drawings is padding with zeros — writing 3 ft 6 in as 3.6 ft when it is 3.5 ft, a 30 mm error. Convert everything to inches first, then divide by 12.
What does a “4 fen” pipe mean in millimetres?
Here “fen” is 1/8 inch, so a 4 fen pipe is 1/2 inch = 12.7 mm, i.e. DN15 with roughly 21.3 mm outside diameter. Note that DN is neither bore nor OD — galvanised steel follows the bore series and plastic follows the OD series, so match fittings on outside diameter, not on the “fen” label.
How different are the Chinese chi and the foot?
One chi is 333.33 mm against 304.8 mm for a foot, so the chi is 9.4% longer. Quotes “by the chi” are common in fit-out work with nobody stating which chi, and a 9% error across tens of metres adds up — confirm and write it on the order.
Cite this page
Use this format in reports, method statements or coursework. The link is permanent.
Building Calculator. Length Unit Converter. 2026-10-25. https://jianzhujisuan.com/en/unit-length
Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.