Calculator
HVAC Load Calculator
Run a Manual J-style load screening on site — enter home size, climate region, insulation, and internal heat gains to get recommended cooling and heating capacity in BTU/hr and tons. Free, no signup.
Free
Total square footage
Conditioned living space only — not garage or attic.
TexasZone 3 (Warm)
Location · Texas · Zone 3 — Warm
Your state sets the IECC climate zone automatically.
Summer (1% design): 102°F · Winter (99% design): 18°F
Dallas, Phoenix, Atlanta, Memphis
Cooling season (May–Sep) — AC and mini-split cooling loads are the priority.
Pre-filled design temps match your state. Change them if your site runs hotter or colder than the state default — whole-building loads use them to fine-tune heating and cooling.
Average ceiling height
2,000 sq ft · Zone 3 (Warm)
Recommended cooling capacity
3.0 tons
34,997 BTU/hr
10.3 kW · ~667 sq ft/ton
- Central AC / heat pump3.0 tons
How we calculated this
- Central AC / heat pump: 3 ton system — standard residential size, rounded up from calculated load.
Cooling load breakdown
- Envelope cooling load27,367 BTU/hr
- Occupant heat gain900 BTU/hr
- Equipment heat gain1,706 BTU/hr
- Lighting heat gain1,024 BTU/hr
- Kitchen heat gain4,000 BTU/hr
- Total34,997 BTU/hr
Recommended size is within 10–15% of calculated load — the sweet spot for comfort and efficiency.
Quick reference
- 1 ton of cooling
- 12,000 BTU/hr
- 1 kW cooling
- 3,412 BTU/hr
- Typical home (2,000 sq ft)
- 2.5–4 ton central AC
- Occupant heat gain
- ~450 BTU/person
- Manual J screening
- ±10–15% typical home
What you'll get
Choose whole building or single room
Whole building runs a Manual J-style screening with envelope, design temps, and internal gains. Single room sizes one zone with a simpler field set.
Enter building or room details
Add square footage, climate region, insulation, windows, and — for whole homes — wall construction, foundation, and optional design temperatures.
Get equipment capacity
See calculated cooling and heating load, recommended tonnage, and a component breakdown you can use to validate contractor quotes.
How it works
- 1
Choose whole building or single room
Whole building runs a Manual J-style screening with envelope, design temps, and internal gains. Single room sizes one zone with a simpler field set.
- 2
Enter building or room details
Add square footage, climate region, insulation, windows, and — for whole homes — wall construction, foundation, and optional design temperatures.
- 3
Get equipment capacity
See calculated cooling and heating load, recommended tonnage, and a component breakdown you can use to validate contractor quotes.
Why HVAC contractors run load calculations on every replacement
Proper HVAC sizing starts with a load calculation. An undersized system cannot maintain comfort on design days; an oversized system short-cycles, wastes energy, and fails to dehumidify. This calculator gives you a Manual J-style screening estimate in the field — before you commit to equipment.
The model accounts for envelope load by climate zone, ceiling height, insulation, sun exposure, window type, occupant heat gain, equipment and lighting loads, and infiltration via air-tightness selection. For final equipment selection on large homes, follow up with a full ACCA Manual J room-by-room calculation.
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View statesLoad Calculator FAQs
How is this different from the BTU Calculator?
The BTU Calculator is optimized for single-room and window-unit sizing. The HVAC Load Calculator defaults to whole-home inputs, adds equipment and lighting internal gains, air tightness, and sunroom/kitchen factors — closer to a contractor Manual J screening workflow.
Is this a full Manual J calculation?
No. This is a simplified screening estimate (±15–20%). A full ACCA Manual J includes room-by-room dimensions, duct location, orientation-specific solar gains, and latent loads. Use this for preliminary sizing and customer conversations; run Manual J software before final equipment purchase.
What units does the load calculator output?
Results show BTU/hr, kilowatts (kW), and standard residential tonnage (1 ton = 12,000 BTU/hr). Heating output includes furnace-size rounding for common nameplate capacities.
Is this HVAC load calculator free?
Yes. Every tool on CloseCrew is free for HVAC contractors — no account required to run calculations.
