Reference
Units & conversions
Every physical quantity Open Gauge supports, its SI storage unit, and the display-unit conversion factors.
All stored numeric values in Open Gauge's database are in SI units. The unit you pick in the UI (e.g. °C, kPa, psi) is a display unit — Open Gauge converts to/from SI at the boundary, and stores the display unit alongside the value so it can round-trip correctly.
| Physical quantity | SI unit | Display units → SI |
|---|---|---|
| Temperature | K | °C → K = °C + 273.15 · °F → K = (°F − 32) × 5/9 + 273.15 |
| Pressure | Pa | kPa ×1,000 · MPa ×1,000,000 · bar ×100,000 · psi ×6,894.757 · hPa ×100 · atm ×101,325 · mmHg ×133.322 · inHg ×3,386.389 · inH₂O ×249.0889 |
| Flow (volumetric) | m³/s | m³/h ÷3,600 · L/min ÷60,000 · gal/min (US) ×6.309×10⁻⁵ |
| Flow (mass) | kg/s | kg/h ÷3,600 · g/min ÷60,000 · lb/min ×0.00755987 |
| Level | m | mm ÷1,000 · cm ÷100 · in ×0.0254 · ft ×0.3048 · % (application-dependent) |
| Humidity | %RH | g/m³ (no universal conversion) · dew point (requires psychrometric calculation) |
| Force | N | kN ×1,000 · kgf ×9.80665 · lbf ×4.44822 |
| Torque | N·m | kgf·m ×9.80665 · lbf·ft ×1.35582 |
| Mass | kg | g ÷1,000 · mg ÷1,000,000 · lb ×0.45359237 |
| Strain | m/m | µε ×10⁻⁶ |
| Displacement | m | nm ×10⁻⁹ · µm ×10⁻⁶ · mm ×10⁻³ · cm ×10⁻² · in ×0.0254 · ft ×0.3048 |
| Angle | rad | ° × π/180 |
| Angular velocity | rad/s | rpm × 2π/60 · °/s × π/180 |
| Angular acceleration | rad/s² | °/s² × π/180 |
| Velocity | m/s | km/h ÷3.6 · mph ×0.44704 · knots ×0.514444 |
| Acceleration | m/s² | g ×9.80665 |
| Sound pressure | Pa | dB/dBA/dBC are logarithmic scales — not directly convertible without a reference pressure |
| Voltage | V | mV ÷1,000 · kV ×1,000 |
| Current | A | mA ÷1,000 · kA ×1,000 |
| Resistance | Ω | kΩ ×1,000 · MΩ ×1,000,000 |
| Power | W | kW ×1,000 · MW ×1,000,000 |
| Energy | J | Wh ×3,600 · kWh ×3,600,000 · MWh ×3,600,000,000 |
| Frequency | Hz | kHz ×1,000 · MHz ×1,000,000 · GHz ×1,000,000,000 · bpm ÷60 |
| Capacitance | F | µF ×10⁻⁶ · nF ×10⁻⁹ · pF ×10⁻¹² |
| Inductance | H | mH ×10⁻³ · µH ×10⁻⁶ |
| Impedance | Ω | kΩ ×1,000 · MΩ ×1,000,000 |
| Magnetic field | T | mT ×10⁻³ · µT ×10⁻⁶ · G ×10⁻⁴ |
| Electric field | V/m | kV/m ×1,000 |
| Radiation | Gy (absorbed dose) | Sv is equivalent dose (not directly convertible) · rem → Sv ×0.01 · Bq is activity (a different quantity) |
| Illuminance | lx | foot-candle ×10.7639 |
| Luminance | cd/m² | — |
| Concentration | mol/m³ | ppm, ppb, %, mg/m³ depend on substance — requires molecular weight and conditions |
| pH | dimensionless | — |
| Conductivity | S/m | mS/cm ×0.1 · µS/cm ×0.0001 |
| Salinity | kg/m³ | g/L (numerically identical) |
| Dissolved oxygen | mg/L | % saturation requires temperature and pressure |
| Oxidation-reduction potential | V | mV ÷1,000 |
| Density | kg/m³ | g/cm³ ×1,000 |
| Viscosity | Pa·s | cP ×0.001 |
| Moisture | kg/kg | % ÷100 |
| Particle concentration | particles/m³ | particles/ft³ ×35.3147 |
| Wind direction | rad | ° × π/180 |
| Precipitation | m | mm ÷1,000 · in ×0.0254 |
| Blood oxygen | % | — |
| Surface roughness | m | µm ×10⁻⁶ |
Some quantities (sound pressure, radiation, concentration) are noted above as not universally convertible — Open Gauge stores whatever the user entered for these without attempting a lossy conversion, since a correct conversion needs additional context (a reference value, molecular weight, measurement conditions) that isn't always available.