Chiller & HVAC Field Calculators
Convert temperature between Fahrenheit and Celsius.
Choose the temperature scale you have. The result automatically converts to the other scale.
Advanced
Formula: °C = (°F − 32) × 5 ÷ 9. °F = (°C × 9 ÷ 5) + 32.
Assumptions: Direct temperature scale conversion.
Warnings: Confirm units before comparing readings or manuals.
Convert water pressure and head across US and metric field units.
Choose the unit you have, enter the value, then choose the output unit. Feet of water is the default output.
Advanced
Formula: This converter uses PSI as the common reference. 1 psi ≈ 2.31 ft H₂O, 27.72 in. w.c., 6.8948 kPa, 0.06895 bar, 0.0703 kg/cm², 0.704 m H₂O, and 704 mm H₂O.
Worldwide units covered: PSI, feet of water, inches water column, kPa, bar, kg/cm², meters of water, and millimeters of water.
Assumptions: Water-based field conversion using standard density approximations. Feet of water is the default output, but the output dropdown can show any covered unit.
Warnings: Glycol, density, temperature, elevation, and measurement conditions can change exact pressure-head relationships.
Convert gauge pressure and absolute pressure.
Choose whether your pressure is gauge pressure or absolute pressure.
Advanced
Formula: PSIA = PSIG + 14.7. PSIG = PSIA − 14.7.
Assumptions: Uses 14.7 psia as standard atmospheric pressure.
Warnings: Site atmospheric pressure changes with elevation and weather. Use site atmospheric pressure when precision matters.
Convert vacuum and pressure units using absolute pressure as the common reference.
Enter one vacuum or pressure value and select the units.
Advanced
Formula: Uses absolute pressure as the common reference. Standard atmosphere is treated as 14.7 psia, 760 torr, and 1 psi = 2.036 in Hg.
Assumptions: Inches Hg vacuum increases as pressure drops below atmosphere. Microns are absolute pressure.
Warnings: Lower microns mean deeper vacuum. Positive PSIG is pressure above atmosphere, not vacuum.
Calculate discharge absolute pressure divided by suction absolute pressure.
Choose PSIG or PSIA, then enter suction and discharge pressure.
Advanced
Formula: Compression ratio = discharge absolute pressure ÷ suction absolute pressure.
Assumptions: Compression ratio always uses absolute pressure. If PSIG is entered, 14.7 is added first.
Warnings: Do not calculate compression ratio directly from gauge pressure without converting to absolute pressure.
Calculate refrigerant superheat from measured suction-line and saturation temperatures.
Enter the measured line temperature and the applicable saturation temperature.
Advanced
Formula: Superheat = suction-line temperature − evaporator saturation temperature.
Blended refrigerants: Use dew-point saturation temperature for superheat.
Warnings: Compare the result with the applicable equipment design, operating condition, measurement location, and manufacturer expectation.
Calculate refrigerant subcooling from measured liquid-line and saturation temperatures.
Enter the measured line temperature and the applicable saturation temperature.
Advanced
Formula: Subcooling = condenser saturation temperature − liquid-line temperature.
Blended refrigerants: Use bubble-point saturation temperature for subcooling.
Warnings: Compare the result with the applicable equipment design, operating condition, measurement location, and manufacturer expectation.
Find the temperature difference between two field readings.
Use entering and leaving temperatures from the same circuit or component.
Advanced
Formula: Delta T = entering temperature − leaving temperature.
Assumptions: Readings are from the same side of the system and the same operating condition.
Warnings: Unexpected negative Delta T usually means measurement points, flow direction, or labels need to be checked.
Estimate outdoor wet-bulb temperature from dry-bulb temperature and relative humidity.
Use outdoor dry-bulb temperature and relative humidity.
Advanced
Formula: Uses a common wet-bulb estimate formula based on dry-bulb temperature and relative humidity.
Assumptions: The output is an estimate, not a measured wet-bulb reading.
Warnings: For tower control, commissioning, or performance verification, use a measured wet-bulb reading when accuracy matters.
Estimate static pressure from vertical water-column height.
Use vertical height from the pressure point to the top of the water column.
Advanced
Formula: Static pressure = vertical height × fluid density × 0.052.
Assumptions: Static pressure only. Pump pressure, flow loss, and pressure drop are not included.
Warnings: Use vertical height, not pipe length. Fluid density changes with glycol and temperature.
Calculate pump differential pressure and head from suction and discharge pressure.
Use suction and discharge pressures taken at comparable elevations when possible.
Advanced
Formula: Differential pressure = discharge PSI − suction PSI. Pump head = differential pressure × 2.31.
Assumptions: The 2.31 factor assumes water. Comparable elevation matters.
Warnings: If discharge pressure is below suction pressure, verify gauge locations, flow direction, and readings.
Calculate pressure drop and head loss across a component.
Use pressures from the entering and leaving side of the same component.
Advanced
Formula: Pressure drop = entering PSI − leaving PSI. Head loss = pressure drop × 2.31.
Assumptions: The 2.31 head-loss factor assumes water and readings taken across the same component.
Warnings: This calculator does not diagnose the cause of pressure drop.