You know the number. The plan is in metres, the tape reads feet, the ticket says tons, and the curing spec is in Fahrenheit. This converter moves one jobsite measurement across the metric and imperial units without changing the measurement itself.
How do you convert a jobsite unit?
Pick the quantity type, enter the value, and choose the unit it is in and the unit you need. The converter prints the converted value plus every equivalent in that quantity type, and it states the exact definition it used under the result.
Converted value = entered value × exact from-unit factor ÷ exact to-unit factor
There are no defaults to set and no allowance to add. A unit conversion is exact by definition, so the only thing that can be wrong is entering the wrong number or the wrong unit.
Which units does the converter cover?
| Quantity type | Units | Jobsite use |
|---|---|---|
| Length | mm, cm, m, km, in, ft, yd, mi | Plan dimensions, tape readings, cut lengths |
| Area | mm², cm², m², ha, km², in², ft², yd², acre, mi² | Slab and lot areas, coverage areas |
| Volume | mL, L, m³, in³, ft³, yd³, US gal, US fl oz | Pour volumes, drums, small batches |
| Weight | g, kg, metric tonne, oz, lb, US short ton | Ticket weights, material weights |
| Temperature | °C, °F | Curing specs, weather limits |
Which conversions are exact?
Every factor the converter uses is a definition, not a measurement. Definitions never drift, so every converter on earth that uses the same definitions gives the same answers.
| Relationship | Constant used | Where it applies |
|---|---|---|
| 1 in = 0.0254 m | Exact | All imperial length entries |
| 1 ft = 0.3048 m | Exact | All imperial length entries |
| 1 yd = 0.9144 m | Exact | All imperial length entries |
| 1 mi = 1609.344 m | Exact | All imperial length entries |
| 1 ft² = 0.09290304 m² | Exact (0.3048²) | All imperial area entries |
| 1 yd² = 0.83612736 m² | Exact (0.9144²) | All imperial area entries |
| 1 acre = 4046.8564224 m² | Exact (43,560 ft²) | Lot and land area entries |
| 1 ft³ = 0.028316846592 m³ | Exact (0.3048³) | All imperial volume entries |
| 1 yd³ = 0.764554857984 m³ | Exact (0.9144³) | All imperial volume entries |
| 1 US gal = 0.003785411784 m³ | Exact (231 in³) | Drum and liquid entries |
| 1 lb = 0.45359237 kg | Exact | All imperial weight entries |
| 1 US short ton = 907.18474 kg | Exact (2,000 lb) | Ticket weight entries |
| °C = (°F − 32) × 5/9; °F = °C × 9/5 + 32 | Exact | All temperature entries |
NIST Handbook 44 Appendix C and NIST Guide to the SI Appendix B supply the cited factors. The result line under the converter names the exact definition behind each calculation, so a plan checker can re-derive the number.
Worked imperial example
A plan dimension reads 6 ft and the cut list is in metres.
- Metres: 6 × 0.3048 = 1.8288 m.
- Centimetres: 1.8288 × 100 = 182.88 cm.
- Inches: 1.8288 ÷ 0.0254 = 72 in.
Converted result: 1.8288 m, 182.88 cm, 72 in. No rounding is applied during the calculation; the display shows up to 4 decimal places.
Worked metric example
A lot measures 1 acre and the coverage sheet is in square metres.
- Square metres: 1 × 4046.8564224 = 4046.8564224 m².
- Square feet: 4046.8564224 ÷ 0.09290304 = 43,560 ft².
- Hectares: 4046.8564224 ÷ 10,000 = 0.40468564224 ha.
Converted result: 4046.856 m², 43,560 ft², 0.405 ha. The 43,560 ft² check confirms the factor: an acre is defined as 43,560 square feet.
Worked temperature example
A curing spec requires 20 °C and the site thermometer reads Fahrenheit.
- Fahrenheit: 20 × 9/5 + 32 = 68 °F.
- Reverse check: (68 − 32) × 5/9 = 20 °C.
Converted result: 68 °F. Temperature is the one type with an offset rather than a pure factor, and the converter rejects anything below absolute zero (−273.15 °C).
Which foot does the converter use?
The converter uses the international foot: 1 ft = 0.3048 m exactly. NIST retired the US survey foot on 1 January 2023, so the international foot is now the foot in all applications except historic and legacy survey records.
The survey foot (0.3048006096 m) differs from the international foot by about 2 parts per million. That gap is invisible on a tape measure but real on a long survey traverse. If the number comes from a legacy survey record in survey feet, confirm the unit with the surveyor before converting.
Why can't you reuse a length factor for area or volume?
Area and volume factors are the length factors squared and cubed. Using the length factor 0.3048 to convert square metres to square feet gives the wrong answer by a factor of 0.3048.
| Task | Correct factor | Wrong reuse |
|---|---|---|
| 100 m² to ft² | 100 ÷ 0.09290304 = 1076.391 ft² | 100 ÷ 0.3048 = 328.084 (wrong) |
| 5 m³ to yd³ | 5 ÷ 0.764554857984 = 6.540 yd³ | 5 ÷ 0.9144 = 5.468 (wrong) |
The converter keeps separate exact factors for each quantity type, so this mistake cannot happen inside the tool. When converting by hand, square the length factor for area and cube it for volume.
Common conversion mistakes
- Converting square metres with the metres-to-feet factor (3.28) instead of the area factor.
- Reading a ton ticket as short tons when the supplier meant metric tonnes, or the reverse.
- Using the US gallon factor for an Imperial-gallon figure; the Imperial gallon is 4.54609 L, a different unit this converter does not cover.
- Entering a legacy survey-foot record as international feet.
- Rounding the entered value before converting, then blaming the conversion for the drift.
- Treating a converted weight as proof of a legal vehicle load; payload is a separate transport check.
- Adding waste or allowance inside the conversion; the conversion changes the unit, never the quantity.
What the converter does not do
The converter changes units through exact definitions. It does not measure the job, pick the unit the plan should have used, or resolve which unit a supplier ticket meant.
Three units stay out of the tool on purpose. The retired US survey foot belongs to legacy survey records, not current conversions. The Imperial gallon is a different unit from the US gallon. The long ton (1016.047 kg) appears on some import paperwork and is not a jobsite ticket unit in the US. When a ticket's ton or gallon basis is unclear, the supplier ticket reading guide shows how to confirm the basis before converting.
For quantities that start from a material rather than a dimension, use the material-specific converters: the Concrete Units Calculator for a known concrete quantity, and the aggregate weight-volume converter for stone and sand.
Sources and scope
- NIST Handbook 44 (2026), Appendix C: exact inch, foot, yard, and mile definitions and derived area and volume relationships; accessed 21 October 2026.
- NIST Guide to the SI, Appendix B: acre, US gallon, US fluid ounce, avoirdupois pound and ounce, short ton, and temperature conversion factors; accessed 21 October 2026.
- NIST, "Putting the Best 'Foot' Forward: Ending the Era of the U.S. Survey Foot": the international foot (1 ft = 0.3048 m exactly) supersedes the US survey foot in all applications from 1 January 2023; accessed 21 October 2026.
Source scope: NIST supports the stated definitions and the survey-foot retirement. Definitions do not measure the job, resolve an ambiguous ticket unit, or set an allowance. Project drawings, specifications, supplier records, local rules, and responsible people control the measurement, the unit a ticket means, and the final project quantity.
Review note: Calculation logic and independent automated fixtures passed internal review. Saleem Sial is the research and editorial owner. Waseem Sial, External Reviewer and Engineer, remains listed for ongoing external review; no completed external-review date is claimed.
