HVAC Calculators

What it does: Enter line temps and pressures, pick your refrigerant, and get superheat and subcooling with an undercharged / overcharged / restriction diagnosis.

Example: R-410A with a 45°F evaporator saturation temp and a 57°F suction line reads 12°F superheat — right in the 8–14°F TXV target.

What it does: Dial in a fixed-orifice system with the Carrier target-superheat method and check compression ratio against healthy operating ranges.

Example: 365 psig discharge with 118 psig suction gives a (365+14.7)/(118+14.7) = 2.9:1 compression ratio, inside the healthy 2.5–3.5:1 band.

What it does: Turn available static pressure and total equivalent length into a friction rate, then a recommended round diameter and equivalent rectangular sizes.

Example: 400 CFM held to a 900 FPM supply target sizes to about a 9-inch round duct (64 sq in of area).

What it does: Find CFM from BTU and ΔT, velocity, or velocity pressure, and compare total external static pressure against the 0.50 iwc target.

Example: A 3-ton system should move about 1,200 CFM (~400 CFM/ton); at a 20°F rise that's 1.08 × 1,200 × 20 = 25,920 BTU/hr sensible.

What it does: Convert CFM and temperature/enthalpy differences into sensible, latent, and total capacity, plus a rough square-foot starting estimate.

Example: 600 sq ft × ~30 BTU/sq ft ≈ 18,000 BTU/hr (1.5 tons) — a ballpark only; confirm every job with a full Manual J.

What it does: Solve Q = 500 × GPM × ΔT for heat transfer, or work backward from a target load and temperature drop to the GPM you need.

Example: 10 GPM across a 20°F ΔT moves 500 × 10 × 20 = 100,000 BTU/hr; at a 10°F ΔT expect roughly 2.4 GPM per ton.