300 sq ft room
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.
AC tonnage = cooling BTU/hr ÷ 12,000. A 300 sq ft room in a mixed climate often needs about 2–2.5 tons with average insulation.
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.
AC tonnage = cooling BTU/hr ÷ 12,000. A 300 sq ft room in a mixed climate often needs about 2–2.5 tons with average insulation.
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.
| Floor area | Cooling BTU | Tons |
|---|---|---|
| 200 sq ft | 5,000 | 0.4 |
| 400 sq ft | 10,000 | 0.8 |
| 600 sq ft | 15,000 | 1.3 |
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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Divide cooling BTU/hr by 12,000 — e.g. 24,000 BTU/hr = 2 tons.
Often 2.5–3.5 tons depending on climate, insulation, and layout — use room-by-room estimates for accuracy.
No — oversized units short-cycle, cool unevenly, and remove less humidity than a properly sized system.
Central systems serve multiple rooms; zoned or ductless setups size each zone separately.
Higher SEER lowers electricity use but sizing (tons) must match load first — pair with the Window AC Cost Calculator for operating cost.
Use it for planning and contractor conversations — final equipment selection should include a professional load calculation.
AC tonnage inputs — room size, climate zone, and insulation — are processed only in your browser and are never sent to EverydayTools servers.
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.
Standard ceiling is 8 ft