HVAC Calculators
Free HVAC Calculators
Load sizing with climate-zone-adjusted BTU calculations and refrigerant diagnostics with full pressure-temperature interpolation. Built for HVAC contractors and technicians.
BTU / HVAC Load Calculator
Calculate cooling and heating load by climate zone, insulation, windows, and duct location. Whole-house or room-by-room breakdown with automatic tonnage sizing.
A2L supportSuperheat & Subcooling Calculator
Check charge level with PT interpolation for 10 refrigerants including R-454B and R-32. Four-quadrant diagnostic decision tree with TXV and fixed orifice targets.
New rule 2026EPA Refrigerant Leak Rate Calculator
The AIM Act leak repair rule took effect January 1, 2026. Annualizing and rolling average methods, 10/20/30 percent thresholds, repair deadlines, and ALD checks per 40 CFR 84.106.
A2L complianceA2L Charge Limit Calculator
Maximum R-454B and R-32 charge for a room, or minimum room area for a charge, per UL 60335-2-40 and ASHRAE 15.2. Verified against Daikin, York, and ASHRAE published tables.
A2L complianceA2L Line Set Calculator
Size the liquid and suction line set by tonnage and length, and get a REUSE, FLUSH, or REPLACE verdict for an existing R-410A set with R-454B or R-32. Charge, drier, and evacuation specs cited.
50+ brandsSerial Number Lookup
How old is that unit? Decode the manufacture date from the serial for 50+ brands, with the refrigerant era and warranty context for the decoded year.
DecoderTonnage From Model Number
Paste any AC or heat pump model number and get nominal tonnage, BTU/h, and SEER and refrigerant hints. Brand schemes for 40+ brands plus the universal divisible-by-6 rule.
Superheat & Subcooling by Refrigerant
Frequently Asked Questions
Are these HVAC calculators free?
Yes. Every calculator is completely free: no login, no email gate, no ads. We build these tools because they help trade contractors do better work. If a number is wrong we want to hear about it. Accuracy is the whole point.
How accurate is the BTU calculator?
The BTU calculator uses ACCA Manual J simplified methodology with ASHRAE-referenced base values and IECC climate zones. It is an estimate for planning purposes, not a substitute for a professional Manual J calculation required for permits and equipment selection. Results are typically within 15-20% of a detailed Manual J.
Which refrigerants does the superheat calculator support?
The calculator includes R-410A, R-407C (with zeotropic glide handling), R-134a, R-404A, R-22 (legacy), R-454B (Puron Advance), R-32, R-448A, R-449A, and R-290 (propane). PT tables are sourced from published manufacturer charts (Chemours, Honeywell, Hudson Technologies, National Refrigerants, Carrier) and every table is cross-checked against a second published source.
More math off your plate.
Size the system with the BTU calculator, verify the charge with superheat and subcooling, then make sure the invoice actually covers your overhead.