CFM for 3-ton AC?
About 1,200 CFM using the 400 CFM per ton rule of thumb.
Heat pump sizing balances cooling tons and heating BTU/hr from the same room load model — verify balance point and backup heat for your climate.
Use the calculator form above with your room size, system capacity, or appliance usage. Results update instantly in your browser — no data is sent to a server.
Concise answers for common searches — definitions, steps, and comparisons.
About 1,200 CFM using the 400 CFM per ton rule of thumb.
12,000 BTU/hr of cooling capacity equals one ton of refrigeration.
Heat pump sizing balances cooling tons and heating BTU/hr from the same room load model — verify balance point and backup heat for your climate.
Formula
See calculator inputs and results panel for step-by-step math.Select imperial/metric, rectangle vs area, tons vs BTU, or usage presets as shown.
Type room dimensions, system tonnage, CFM, appliance watts, or electric rate.
Pick climate zone 1–5 and insulation quality for load-based calculators.
Use BTU/hr, tons, CFM, duct diameter, or seasonal cost in the results panel.
Copy results or share a link with your HVAC contractor or energy auditor.
Use Duct CFM, Duct Size, or Energy Cost calculators for a complete HVAC plan.
Input
20×15 ft · 8 ft ceiling · zone 3Output
≈ 7,500 BTU/hr cooling300 sq ft × 25 BTU/sq ft × average insulation × 1.0 height factor.
Input
2.5 tonsOutput
1,000 CFM2.5 × 400 CFM/ton = 1,000 CFM supply airflow rule of thumb.
Common real-world scenarios where this tool saves time.
12×15 ft room, zone 3, average insulation → ~9,000–11,000 BTU/hr cooling load.
2,000 sq ft home, zone 4 → ~3.5–4 tons cooling with average insulation.
3-ton system → 1,200 CFM target → 14" round trunk at 700 FPM velocity.
900 W unit, 8 hr/day, 90 days at $0.16/kWh → seasonal cost estimate for budgeting.
Step-by-step chains that connect related tools for common tasks.
From room BTU to duct airflow and diameter.
Compare portable appliance electricity spending.
| Tons | Cooling BTU/hr | Typical use |
|---|---|---|
| 1.5 | 18,000 | Small zone / condo |
| 2.5 | 30,000 | Medium room or zone |
| 3.5 | 42,000 | Large open area |
Rule-of-thumb sizing is a starting point — ACCA Manual J is the industry standard.
Undersized ducts reduce efficiency and comfort even when tonnage is correct.
Include climate zone, insulation, ceiling height, and sun exposure — or request Manual J.
Check heating BTU/hr and balance point, not just cooling tons.
Compressors cycle — actual kWh may be lower than watts × hours suggests.
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Size in tons from cooling BTU load — ensure rated heating BTU/hr meets your climate at outdoor design temperature.
Modern cold-climate heat pumps work below 0°F with reduced capacity — verify manufacturer ratings for your zone.
Cooling tons use the same 12,000 BTU/ton rule; heating capacity varies by model and outdoor temperature.
SEER measures cooling efficiency; HSPF measures heating season performance — both matter for annual operating cost.
Mini-splits size each zone separately; ducted systems use whole-home load — this tool estimates one zone or room.
Many cold-climate installs add electric resistance or furnace backup — confirm with your installer for your design temperature.
Heat pump room and climate inputs are handled in-browser only — EverydayTools does not transmit heat-pump-size calculator data.
Estimates only — not professional HVAC or energy audit advice. Verify with a licensed contractor before purchasing equipment.
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Reviewed on 2026-06-28.
Same workflow or intent — pick the next step without leaving the site.
Free duct cfm calculator: Calculate required duct airflow in CFM from AC tonnage or cooling BTU/hr using the common 400 CFM per ton residential ru Runs locally in your browser — no signup.
Free BTU room calculator: floor area, ceiling height, climate zone → cooling BTU/hr, tons, and suggested CFM. Runs locally in your browser.
Free AC tonnage calculator: room size and climate → central air conditioner tons from cooling BTU load. Runs locally in your browser.
Free furnace BTU calculator: room or whole-home sq ft → recommended heating BTU/hr output by climate zone. Runs locally in your browser.
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Standard ceiling is 8 ft