CFM per Ton Calculator — Tons to CFM for AC & Cooling

Read the system's tonnage off the nameplate (or divide total cooling BTU/hr by 12,000), pick the airflow rate that matches your climate — 350 CFM/ton for humid regions, 400 for standard, 450 for dry — and multiply. A 3-ton system at the standard rate moves 3 × 400 = 1,200 CFM. The calculator also runs the direction in reverse: a blower measured at 1,600 CFM is behaving like a 4-ton system, which is how technicians sanity-check an air handler against its spec.

The industry standard is 400 CFM per ton, so a nominal 1-ton system moves 400 CFM of air across the evaporator coil. The rate flexes between 350 and 450 depending on climate and equipment: humid climates drop toward 350 to slow air over the wet coil and squeeze out more moisture, dry climates rise toward 450 for better throw and sensible capacity. Heat pumps usually follow the same cooling-mode numbers.

1 ton = 400 CFM at the standard rate (350–450 across the band). The full ladder: 1.5 tons is 600 CFM (525–675), 2 tons is 800 (700–900), 2.5 tons is 1,000 (875–1,125), 3 tons is 1,200 (1,050–1,350), 3.5 tons is 1,400 (1,225–1,575), 4 tons is 1,600 (1,400–1,800), and 5 tons is 2,000 CFM (1,750–2,250). Every figure scales linearly because tonnage is just capacity per 12,000 BTU/hr and the rate is airflow per unit of capacity.

2,000 CFM at the standard 400 rate — the single most common number on a 5-ton condenser's matching air handler. Verify it two ways: the blower table inside the air handler panel (actual CFM depends on motor type and static pressure), and the temperature split across the coil, which should land near 18–22 °F for a properly matched system. A 5-ton blower delivering 1,700 CFM is telling you static pressure is eating 15% of the design airflow.

No — and the dual rating is the most confusing spec sheet in HVAC. An air handler paired with a 4-ton condenser delivers about 1,600 CFM in cooling. The same cabinet's gas furnace is rated by heating airflow, conventionally 100–130 CFM per 10,000 BTU/hr of heating output, so a 80,000 BTU furnace in the same box may run 1,050–1,300 CFM on heat. Modern variable-speed blowers store both profiles and switch automatically; older single-speed motors were tapped to favor one mode and compromise the other.

Multiply 3.5 by the rate: 3.5 × 400 = 1,400 CFM standard, 1,225 at the humid-climate 350 rate, 1,575 at the dry-climate 450 rate. 3.5 tons is a common real-world size because Manual J load calculations rarely land on round numbers — and it maps to a 1,400 CFM blower setting that most ECM air handlers support directly. Round only at the blower tap, never by oversizing the equipment itself.

Total the system CFM, then distribute it by each room's share of the load — floor area is the common proxy. A 1,200 CFM system serving a 2,000 sq ft house gives 0.6 CFM per sq ft; a 300 sq ft bedroom gets 300 ÷ 2,000 × 1,200 = 180 CFM. The duct run to each room then carries that CFM at duct-design velocity, which is where register count and branch duct sizing come from. The calculator's room split does this arithmetic live.

Because the rate is a latent-vs-sensible dial. In humid climates, slower coil airflow (350) means air spends more time against the cold, wet coil, so the system extracts more moisture per pass — trading a little sensible capacity for drier, more comfortable air. In dry climates there is little moisture to remove, so faster airflow (450) raises sensible efficiency and improves register throw without any humidity penalty. Pick by your design climate, not by habit.

Regla rápida: CFM = toneladas × 400 (tasa estándar). Multiplica las toneladas del sistema por 350, 400 o 450 según el clima — 350 para climas húmedos, 400 estándar, 450 para climas secos. Ejemplos: un sistema de 2 toneladas mueve 800 CFM; uno de 3 toneladas, 1,200 CFM; uno de 5 toneladas, 2,000 CFM. Para hacerlo al revés, divide los CFM del ventilador entre 400 para obtener las toneladas equivalentes. Esta calculadora hace ambas conversiones y reparte el flujo por habitación según los metros cuadrados.

No — and keeping the two apart is deliberate. Tonnage-based sizing (CFM per ton) is how cooling airflow is specified in the field; the BTU-based method uses the sensible-heat equation CFM = BTU/hr ÷ (1.08 × ΔT) and answers a different question: what airflow a given heat flow and temperature split imply. If you need that ΔT method — for duct heaters, furnaces or checking a coil's temperature split — the CFM to BTU calculator on this site handles it step by step.