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HVAC, AC BTU, Dehumidifier, CFM and ACH Calculators
Estimate room AC size, portable AC capacity, dehumidifier pints/day, CFM by ACH, bathroom fan CFM, garage ventilation and HVAC unit conversions with visible formulas and source-backed assumptions.
First-version coverage
- Room and window AC BTU ranges
- Portable AC SACC / label caveats
- Basement and room dehumidifier sizing
- CFM, ACH, bathroom fan and garage ventilation math
- Copy, share URL, CSV export and print/PDF workflow
Calculators
Estimate a room air conditioner BTU range from room size, ceiling height, sun, occupants, kitchen heat and insulation.
Window Air Conditioner Size CalculatorEstimate window AC size and review oversizing, humidity, window fit, CEER/EER, noise, drainage and installation limits.
Portable AC Size CalculatorEstimate portable AC capacity and understand SACC, BTU labels, hose losses, exhaust sealing and product label checks.
AC Tonnage CalculatorConvert BTU per hour to cooling tons and thermal kW without treating the result as central HVAC sizing.
Dehumidifier Size CalculatorEstimate dehumidifier pints/day by room area, dampness level, basement condition, temperature, water intrusion and drain access.
Basement Dehumidifier Size CalculatorEstimate basement dehumidifier size with water intrusion, cool temperature, continuous drain and mold-remediation boundaries.
CFM by ACH CalculatorCalculate CFM from room volume and target ACH while avoiding duct-design and code-compliance claims.
ACH CalculatorCalculate air changes per hour from CFM and room volume.
Bathroom Fan CFM CalculatorEstimate bathroom fan CFM using area and fixture rules plus duct, fan rating and local-code caveats.
Garage Ventilation CalculatorEstimate garage ventilation CFM by ACH with explicit CO, combustion appliance and code-compliance boundaries.
Room Ventilation CalculatorEstimate room ventilation airflow from room volume and target ACH.
BTU to Tons CalculatorConvert BTU/h to cooling tons.
BTU to kW CalculatorConvert BTU/h to thermal kW and explain why it is not electrical input.
Pints to Liters CalculatorConvert dehumidifier pints/day and liters/day while distinguishing capacity from bucket volume.
Guides and worked examples
Guide to how many btu per square foot? with formulas, examples, source notes and professional boundaries.
Why Oversized AC Does Not DehumidifyGuide to why oversized ac does not dehumidify with formulas, examples, source notes and professional boundaries.
Portable AC SACC vs BTUGuide to portable ac sacc vs btu with formulas, examples, source notes and professional boundaries.
30 Pint vs 50 Pint DehumidifierGuide to 30 pint vs 50 pint dehumidifier with formulas, examples, source notes and professional boundaries.
What Size Dehumidifier for Basement?Guide to what size dehumidifier for basement? with formulas, examples, source notes and professional boundaries.
CFM vs ACHGuide to cfm vs ach with formulas, examples, source notes and professional boundaries.
Bathroom Fan CFM GuideGuide to bathroom fan cfm guide with formulas, examples, source notes and professional boundaries.
What Is AC Tonnage?Guide to what is ac tonnage? with formulas, examples, source notes and professional boundaries.
Dehumidifier Pints ExplainedGuide to dehumidifier pints explained with formulas, examples, source notes and professional boundaries.
What Size AC for 150 Sq Ft?Worked room AC sizing example for a 150 sq ft room.
What Size AC for 300 Sq Ft?Worked room AC sizing example for a 300 sq ft room.
What Size AC for 500 Sq Ft?Worked room AC sizing example for a 500 sq ft room.
14,000 BTU Portable AC Room SizePortable AC label interpretation for 14,000 BTU units and SACC caveats.
What Size Dehumidifier for a 1000 Sq Ft Basement?Worked dehumidifier sizing example for a 1000 sq ft basement.
What Size Fan for a Small Bathroom?Worked bathroom fan sizing example for a small bathroom.
Sources and maintained assumptions
Sizing assumptions are centralized and show source URLs, check dates and notes.
- DOE Room Air Conditioners
Checked 2026-05-22. Used for room AC preliminary BTU rule, room-level sizing caveats and oversizing humidity cautions.
- DOE Portable Air Conditioners Test Procedure
Checked 2026-05-22. Used for portable AC SACC / label caveats.
- ENERGY STAR Certified Dehumidifiers
Checked 2026-05-22. Used for pints/day and product rating caveats.
- HVI Bathroom Ventilation
Checked 2026-05-22. Used for residential bathroom fan CFM rules and fixture model.
- ACCA Technical Manuals
Checked 2026-05-22. Used to define Manual J, Manual S and Manual D boundaries.
- EPA Mold and Indoor Air Guidance
Checked 2026-05-22. Used for mold and water intrusion disclaimers.