Engineering Unit Converter — Definition Controlled
Convert force, moment/torque, pressure, length, mass and absolute-temperature scale readings through identified SI or published conventional definitions.
Controlled inputs
Conversion result
Method and quantity boundaries
Absolute temperature: convert the scale reading to kelvins, validate T ≥ 0 K, then convert from kelvins.
- Decimal SI prefixes in this catalogue are exact powers of ten. Display rounding does not make the underlying measurement exact.
- kgf and lbf are force units, not mass units. Pound (lb) and ounce (oz) in the mass category are international avoirdupois units.
- N·m is used for moment of force/torque. Although it has the same dimensions as the joule, this converter does not relabel torque as energy.
- A negative pressure can be meaningful for a gauge or differential quantity. The converter cannot infer or change the reference zero.
- For intervals, Δ°C = ΔK and Δ°F = Δ°R = 1.8 ΔK. Do not enter an interval into the absolute-temperature category.
- The browser uses IEEE 754 binary arithmetic; the displayed result is rounded to at most 12 significant digits. Preserve uncertainty and significant figures from the source measurement.
Definition basis used by the code
| Unit or family | Implemented relation | Status / boundary |
|---|---|---|
| kN, MN, daN; kN·m; kPa, MPa; mm, cm, km; g, mg, t | Exact decimal SI powers of ten | Exact definition |
| kilogram-force (kgf) | 1 kgf = 9.80665 N | Exact conventional standard-gravity definition |
| pound-force (lbf) | 1 lbf = 4.4482216152605 N | Exact at standard gravity from the international pound definition |
| lbf·ft; lbf·in | lbf × exact 0.3048 m or 0.0254 m | Derived from exact definitions; preserves 12 in/ft exactly |
| bar; standard atmosphere | 1 bar = 100000 Pa; 1 atm = 101325 Pa | Exact defined values |
| psi | 4.4482216152605 N ÷ (0.0254 m)² | Derived from exact lbf and inch definitions |
| Torr | 1 Torr = 101325/760 Pa | Exact defined relation |
| mmHg (conventional) | 1 mmHg = 133.3224 Pa | NIST published conventional factor; not an actual mercury-column realization |
| inch, foot, yard, mile | 0.0254 m; 0.3048 m; 0.9144 m; 1609.344 m | Exact international definitions |
| pound, ounce (avoirdupois) | 1 lb = 0.45359237 kg; 1 oz = 1/16 lb | Exact international definitions |
| °C, °F, K, °R absolute readings | t/°C = T/K − 273.15; °F and °R use the exact 9/5 scale relation | Affine scale conversion; T below 0 K rejected |
Evidence and classification
Authoritative SI definitions, decimal prefixes, mechanics-unit distinctions and the exact Celsius/Kelvin relation.
Official BIPM publicationOfficial conversion factors and exact-definition notes for inch, international foot/pound, pound-force, moment of force and temperature scales.
Official NIST table · Official NIST footnotesDistinguishes bar, atmosphere, psi, Torr and conventional/manometer units and supplies their factor classifications.
Official NIST pressure tableExplains absolute zero as the theoretical lower bound for thermodynamic temperature.
Official NIST explainerSources accessed 16 July 2026. This is deterministic unit conversion, not an ISO formula, calibration certificate or measurement-uncertainty calculation.
Interpretation questions
Why does 1 mmHg not equal 1 Torr exactly here?
Torr has the exact relation 1 atm/760. The listed mmHg value is the published conventional conversion factor. A real mercury-column realization also depends on specified physical conditions.
Can I convert gauge pressure to absolute pressure?
No. Unit scaling does not change the reference zero. That transformation additionally needs the applicable local/reference pressure and sign convention.
Can I convert a 20 °C temperature rise by entering 20 °C?
No. An absolute reading and an interval follow different relations because absolute scales contain offsets. Use a dedicated temperature-interval conversion.
Does an exact unit definition make my converted measurement exact?
No. The source measurement, calibration, resolution, uncertainty and significant figures still control the result.
Specialized converters
Revision: 16 July 2026. Result classification: definition-controlled numerical unit conversion.
