Calculators
- HVAC Load CalculatorWhole-house and room-by-room heating and cooling loads in BTU/h, with tonnage and airflow references, from square footage, climate, insulation and occupancy.
- HVAC Tonnage CalculatorConvert cooling load (BTU/hr) or square footage to AC tonnage and recommended unit size.
- BTU CalculatorCooling or heating BTU/h for a room or whole home, adjusted for climate, insulation, sun exposure and occupancy.
- CFM / Airflow CalculatorCalculate required CFM by tonnage, by ACH (air changes per hour), or from room volume and load.
- Duct Size CalculatorRound and rectangular duct dimensions for a target CFM, checked against friction rate and air velocity.
- HVAC Sizing CalculatorEnd-to-end HVAC sizing: cooling load, heating load, nominal tons, CFM and trunk duct size in one flow.
- Heating Load CalculatorWinter heat loss in BTU/h from design temperatures, insulation levels and natural air leakage.
- Free Manual J Calculator (Simplified)Simplified Manual J-style room-by-room estimate of heating, cooling and airflow. A free screening tool, not a full ACCA Manual J report.
- Commercial HVAC Load CalculatorCommercial HVAC load with occupancy loads, equipment heat gain, lighting, ASHRAE 62.1 ventilation, and zone-by-zone distribution.
- Heat Pump Size CalculatorHeat pump size in tons and BTU/h, comparing cooling load with winter heating demand and cold-weather capacity.
- Mini Split Sizing CalculatorDuctless mini split sizing by room: heating and cooling BTU/h matched to common indoor-head sizes.
- AC Size CalculatorCentral air conditioner size in tons and BTU/h from square footage, climate, insulation and occupants.
- Furnace Size CalculatorRequired furnace output and AFUE-adjusted input BTU/h by home size, climate zone and insulation.
- Window AC BTU CalculatorFind the right window or room air conditioner size in BTU for any room size and sun exposure.
- Residential HVAC Load CalculatorWhole-house residential heating BTU/h and cooling tons, with every assumption shown.
- Room Heat Load CalculatorHeating and cooling load for a single room in BTU/h, from walls, windows, insulation and climate.
- Server Room Cooling CalculatorSize cooling for server rooms and data closets from equipment wattage, occupancy, and room heat gain.
- Garage Heating Load CalculatorEstimate winter heat loss through garage walls, roof and overhead door, plus design air leakage.
- ASHRAE Sensible Design Load CalculatorCompare winter and summer sensible heat transfer using UA, outdoor airflow and local design temperatures.
- Dehumidifier Moisture Load CalculatorEstimate water-removal capacity from humid incoming air and internal moisture, in US pints and liters per day.
- Home Ventilation Calculator | ASHRAE 62.2 BaselineCalculate the ASHRAE 62.2-2016 baseline continuous dwelling outdoor-air rate from area and bedrooms.
- SEER2 Savings and Simple Payback CalculatorCompare annual cooling energy on a common SEER2 basis, utility savings and simple upgrade payback.
- HVAC Thermal Capacity Unit ConverterConvert heat flow between BTU per hour, refrigeration tons, thermal kilowatts and International Table kilocalories.
- Printable HVAC Heating Loss WorksheetBuild and print a heating budget from measured surfaces, assembly U-factors and outdoor airflow.
- Data Center Cooling and Redundancy CalculatorConvert IT and other zone heat to sensible duty capacity, then compare equal-module N, N+1 and 2N.
- Gym Cooling Load | People and VentilationEstimate sensible and latent gym cooling from exercise, equipment, envelope gains and humid outdoor air.
- Kitchen Cooling and Make-Up Air Load CalculatorBuild a kitchen cooling subtotal from operating appliance heat, staff, envelope and unconditioned make-up air.
- UPS Room Heat Load | Output kW and EfficiencyCalculate local conversion loss from delivered output kW and efficiency, then add separately identified heat.
- Electrical Panel Heat and Fan Airflow CalculatorConvert component losses to room heat and ideal fan airflow from a permitted temperature rise.
- U-Value and R-Value Heat Transfer CalculatorCalculate surface conduction from assembly U or total R, area and temperatures, with flow direction.
- Psychrometric Cooling Load CalculatorCompare sensible and latent approximations with moist-air enthalpy using temperatures and humidity ratios.
- Duct Static Pressure Budget CalculatorCompare critical-path duct and component losses with available blower pressure at target airflow.
- Wattage to Heat Load | Watts and kW to BTU/hConvert operating equipment power to local sensible heat using quantity and load factor.
- Manual S Equipment Sizing CheckSimplified equipment sizing check for total, sensible, and latent cooling, furnace output, and design-temperature heat pump capacity.
Guides
- What Is HVAC Load Calculation?Understand the three design loads, their units, and the building inputs needed before selecting equipment.
- How to Calculate HVAC Load, Step by StepCollect inputs, check heating and moisture arithmetic, and separate load calculations from equipment selection.
- How to Measure Your Home for HVAC SizingA room and envelope survey checklist with checked area, volume, and opening calculations.
- HVAC Load Calculation Example: A Worked WalkthroughA hypothetical 2,000 sq ft example with explicit assumptions, heating subtotals, and cooling capacity checks.
- The HVAC Load Calculation Formula, ExplainedCheck heat-transfer equations, units, and component arithmetic without adding hidden sizing margins.
- What Size AC Do I Need? Load and Capacity ChecksConvert cooling loads to tons, compare component capacities, and check existing ducts before replacing an AC.
- What Size Furnace Do I Need? Input and Output BTUCheck rated furnace output, AFUE estimates, stages, and blower airflow against a documented heating load.
- What Size Heat Pump Do I Need? A Sizing GuideCheck summer moisture performance, winter output, balance point, and backup capacity for the intended controls.
- What Is Manual J? Inputs, Loads, and Report RequirementsWhat a residential Manual J report contains and how to review its inputs before equipment selection.
- Manual J vs Manual S vs Manual D, ExplainedThe load, equipment, and duct deliverables, with capacity examples and checks between each design step.
- 7 Possible Signs Your AC Is OversizedSeven signs that can point to an oversized AC, the other faults that cause them, and how to confirm with a load check.
- Heat Pump vs Furnace: Which Is Right for You?Cost, climate, efficiency, and comfort compared — plus how to choose for your home.
- HVAC Replacement Cost: Compare Quotes and ScopeCompare replacement quotes on equal scope: equipment, ducts, electrical work, warranties, and confirmed incentives.
- What Size Mini Split Do I Need? Loads and CapacitySize mini-split heads from room loads, minimum output, and winter capacity instead of floor area alone.
- AC Tonnage per Square Foot: Chart and LimitsWhat square-feet-per-ton rules really imply, with checked conversions, and why a load calculation should decide.
- Heat Load Calculation Methods ComparedArea estimates, Manual J, and ASHRAE cooling methods compared by inputs, accuracy, and when to use each.
- Heat Load Units: BTU/h, Watts, kW, and TonsConvert BTU/h, watts, kW, and tons correctly, and keep capacity, electrical input, and energy separate.
- Block Load vs Room-by-Room Manual JWhy equipment is sized from the block load and ducts from room loads, with a checked room-airflow example.
- Is Manual J Required for an HVAC Permit?How to find out whether your jurisdiction requires a Manual J, and what an acceptable report includes.
- AC Short Cycling: Causes and FixesThe real causes of short cycling — oversizing included — and how to fix each.
- Is a Bigger AC Better? Why Oversizing BackfiresBigger isn't better — what oversizing actually costs you.
- What Is SEER2? Ratings and Savings ExplainedWhat SEER2, EER2, and HSPF2 measure, how to verify matched ratings, and how to estimate savings.
- Mini Split vs Central Air: Full ComparisonDuctless vs central AC on cost, efficiency, install, and zoning.
- How to Size Ductwork: A Practical GuideSize ducts by CFM and friction loss — the friction-rate method, step by step.
- HVAC Static Pressure ExplainedWhat static pressure is, why high readings hurt, and how to measure it.
- IECC Climate Zones: County Lookup and HVAC LimitsHow to find your county's IECC climate zone, and why it does not replace local design weather.
- HVAC Design Temperature Explained: 1% and 99%Why load calcs use 1% and 99% design temps, not record highs and lows.
- Heat Pump Payback: Costs, Savings, and AssumptionsEstimate payback from local quotes and modeled operating costs, with sensitivity checks and no expired federal credit.
- Heat Pump Tax Credits in 2026: What Ended and RemainsThe federal 25C and 25D credits ended after 2025. What remains: state rebates, utility programs, and how to verify them.
- HVAC Load Calculation Software: How to ChooseEvaluate calculation tools, report exports, approval, offline use, and data ownership before choosing software.
- HVAC Load Calculation Training: Paths and PracticeTraining paths through ACCA, software providers, and manufacturers, plus exercises that build real skill.
- HVAC Load Calculation Service: Scope and Report ReviewWhat a paid Manual J, S, and D service should deliver, what to send the designer, and red flags in reports.
- Questions to Ask Your HVAC ContractorThe questions that separate a right-sized install from an upsell.
- How to Verify a Contractor's HVAC QuoteCheck a quote for proper sizing and scope before you sign.
- How to Read a Manual J Load Calculation ReportReview assumptions and load summaries, reconcile room totals, and keep a useful PDF record for bids.