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Refrigerant Mass Flow Calculator

How many pounds of refrigerant must circulate to deliver a given capacity? Divide the capacity by the enthalpy the refrigerant picks up in the evaporator.

Method reviewed October 26, 2026. Version 1.0.0. How it works

Your inputs

Unit system

Only refrigerants whose properties agree with independent published tables are offered. R-454B is not offered yet.

The saturation (dew-point) temperature at the suction pressure. Get it from a gauge reading with the refrigerant PT calculator.

Superheat picked up inside the evaporator counts as useful cooling.

The saturation (dew-point) temperature at the discharge pressure.

Result

Refrigerant mass flow
473.2lb/h
Mass flow per ton
2.629lb/min per ton

473 lb/h (2.63 lb/min per ton) of R-410A.

Mass flow per minute
7.89lb/min
Refrigeration effect (enthalpy rise in the evaporator)
76.07BTU/lb
Liquid temperature entering the metering device
89.8°F
Show the working
  1. Liquid entering the metering device = bubble point at the condensing pressure − subcooling
    99.78 − 10 = 89.78 °F; h = 108.4 BTU/lb
  2. Vapour leaving the evaporator (saturation + superheat)
    40 °F + 10 °F; h = 184.4 BTU/lb
  3. Refrigeration effect = h(leaving) − h(entering); the expansion keeps enthalpy constant
    184.4 − 108.4 = 76.07 BTU/lb
  4. Mass flow = capacity ÷ refrigeration effect
    36,000 ÷ 76.07 = 473.2 lb/h

The refrigeration effect

Liquid enters the metering device and leaves as a cold mix of liquid and vapour with the same enthalpy. In the evaporator it boils and picks up heat until it leaves as vapour, usually with some superheat. The enthalpy rise between those two points is the refrigeration effect, in BTU per pound.

Mass flow = capacity ÷ refrigeration effect. Subcooling the liquid lowers its enthalpy and raises the refrigeration effect, so less refrigerant has to circulate per ton.

Where the property data come from

Enthalpies are generated with CoolProp, an open-source property library, for the four refrigerants this site validates. They were checked against the NIST Chemistry WebBook for R-134a, R-22 and R-32 (agreement about 0.001 %) and against Arkema’s REFPROP-based R-410A table (about 0.1 %). R-454B is not offered.

Worked example

These are the example values the calculator opens with, and the result the engine calculates for them.

Inputs

Refrigerant
R-410A
Cooling capacity
36,000 BTU/h
Saturated evaporating temperature
40 °F
Superheat leaving the evaporator
10 °F
Saturated condensing temperature
100 °F
Liquid subcooling
10 °F

Result

Refrigerant mass flow
473.2 lb/h
Mass flow per ton
2.629 lb/min per ton
Mass flow per minute
7.89 lb/min
Refrigeration effect (enthalpy rise in the evaporator)
76.07 BTU/lb
Liquid temperature entering the metering device
89.8 °F

473 lb/h (2.63 lb/min per ton) of R-410A.

Assumptions

  • Steady flow; the metering device keeps enthalpy constant; liquid enthalpy is taken as saturated liquid at the liquid temperature.
  • Saturated temperatures are dew points (for R-410A, the bubble point at the condensing pressure sets the liquid temperature).
  • Properties generated with CoolProp 8.0.0 and checked against NIST WebBook (R-134a, R-22, R-32) and Arkema’s REFPROP-based R-410A table.

Limitations

  • Pressure drops in the lines and coils are ignored.
  • For sizing a metering device or lines, use the manufacturer’s data; this tool gives the thermodynamic mass flow only.

Frequently asked questions

How much R-410A flows per ton?

At 40 °F evaporating with 10 °F superheat and 100 °F condensing with 10 °F subcooling, about 2.6 lb per minute per ton.

Does this size my lines or metering device?

No. It gives the thermodynamic mass flow; line and metering-device sizing come from the manufacturer’s data.

Which temperatures should I enter?

The saturated (dew-point) temperatures at the suction and discharge pressures. The refrigerant PT calculator converts gauge readings.

Sources

  1. CoolProp — open-source thermophysical property library (version 8.0.0) — CoolProp developers (MIT licence). Equations of state for pure fluids and mixtures, incompressible fluids and brines, and IAPWS-IF97 water/steam; free for commercial use under its licence. Used here to generate the refrigerant saturation tables.
  2. Ideal-cycle property tables: generator and validation (packages/calc/reference/b7-g4/generate_g4_data.py) — FreeHVACCalculators.com. CoolProp 8.0.0 tables of liquid and vapor enthalpy, isentropic work and discharge temperature; agree with NIST WebBook (R-134a, R-22, R-32) to 0.001 % and with Arkema/REFPROP R-410A to 0.1 %; interpolation error under 0.15 %.
  3. NIST Chemistry WebBook, SRD 69 — saturation tables and isobars for R-134a, R-22 and R-32 — National Institute of Standards and Technology. Ideal cycle check, 40 °F evaporating / 100 °F condensing: refrigeration effect 63.702, 68.810 and 105.419 Btu/lb and isentropic work 9.169, 9.858 and 15.653 Btu/lb (thermochemical Btu) for R-134a, R-22 and R-32; discharge 106.53, 126.65 and 144.82 °F.
  4. Forane 410A Thermodynamic Properties (Saturation), English units — Arkema (generated with NIST REFPROP 9.0). R-410A saturated enthalpies: liquid 88.97 / vapor 181.80 Btu/lb at 40 °F; liquid 112.82 / vapor 183.13 Btu/lb at 100 °F (used only for comparison).

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