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HVAC Calculators

Preliminary HVAC planning calculators

HVAC calculators for AC BTU, dehumidifier size, and CFM / ACH

Enter room conditions and review formula-backed estimates that update as you edit.

Preliminary planning only — verify final HVAC decisions with local code, product manuals and qualified review.

Estimate room AC BTU from size and conditions

Expected output: BTU/h range, common AC sizes and tonnage context

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Inputs

Results update automatically as you edit valid inputs.

Bathroom fan CFMPortable AC sizingACH from CFMContractor questions

Task paths

Choose the workflow that matches your HVAC question

Each path connects a starting calculator, guide pages, worked examples and the final verification questions so users do not land on an isolated page.

Prepare contractor questions
Room cooling sizing flowMove from measured room inputs to AC BTU range, window or portable AC label checks, oversizing risk and printable comparison notes.12 connected stepsMoisture control flowMove from dampness observations to dehumidifier capacity, pints/day class, basement-specific warnings, drainage planning and moisture-source escalation.9 connected stepsAirflow and ventilation flowMove from room volume to CFM, ACH, bathroom exhaust and garage ventilation caveats while keeping code and safety boundaries explicit.9 connected stepsCapacity conversion flowMove between BTU/h, tons and thermal kW for comparison while keeping conversion math separate from equipment sizing approval.5 connected steps

Core HVAC calculators

Open a dedicated calculator page when you want the same workflow with full guide sections, FAQ and source notes.

Open planning questions
Room AC BTU Calculator

Estimate a room air conditioner BTU range from room size, ceiling height, sun exposure, occupants, kitchen heat and insulation, then compare common AC sizes.

Window Air Conditioner Size Calculator

Estimate a window AC BTU range and review oversizing, humidity, window fit, CEER/EER, noise, drainage and installation checks before buying.

Portable AC Size Calculator

Estimate portable AC capacity from room inputs and understand SACC, ASHRAE BTU labels, hose losses, exhaust sealing and product label checks.

AC Tonnage Calculator

Convert BTU per hour to cooling tons and thermal kW while keeping room estimates separate from central HVAC system sizing.

Dehumidifier Capacity and Size Calculator

Estimate dehumidifier capacity in pints per day from room area, dampness, basement condition, temperature, water intrusion and continuous drain access.

Basement Dehumidifier Size Calculator

Estimate basement dehumidifier size with dampness level, cool-temperature adjustment, water intrusion checks and continuous-drain planning.

Guides and worked examples

How Many BTU Per Square Foot?

Plain-English guide to how many btu per square foot? with formula notes, examples, source context and a related calculator.

Why Oversized AC Does Not Dehumidify

Plain-English guide to why oversized ac does not dehumidify with formula notes, examples, source context and a related calculator.

ASHRAE vs SACC Portable AC BTU Ratings

Compare ASHRAE BTU and DOE SACC ratings for portable air conditioners, why SACC is lower, and how to use adjusted capacity when sizing a room.

30 Pint vs 50 Pint Dehumidifier

Plain-English guide to 30 pint vs 50 pint dehumidifier with formula notes, examples, source context and a related calculator.

What Size AC for 150 Sq Ft?

Worked room AC sizing example for a 150 sq ft room with adjustment notes for sun, occupants, ceiling height and kitchen heat.

What Size AC for 300 Sq Ft?

Worked room AC sizing example for a 300 sq ft room with common-size context and oversizing notes.

What Size AC for 500 Sq Ft?

Worked room AC sizing example for a 500 sq ft room, including common AC size comparison and humidity caveats.

14,000 BTU Portable AC Room Size

Portable AC label interpretation for 14,000 BTU units, SACC ratings, hose losses and realistic room-size comparison.

Published by YmirTool. Sources last checked 2026-05-30; page content last updated 2026-06-06. Educational preliminary planning only.

Sources and maintained assumptions

Sizing assumptions are centralized and show source URLs, check dates and notes relevant to this page.

  • DOE Room Air Conditioners

    Checked 2026-05-30. Used for the 20 BTU per square foot room AC starting point and for caveats that room height, climate, shading and windows can move the estimate.

  • ENERGY STAR Room Air Conditioners

    Checked 2026-05-30. Used for room AC adjustment context: reduce capacity for heavy shade, increase for very sunny rooms, and add capacity for additional occupants.

  • DOE Portable Air Conditioners Test Procedure

    Checked 2026-05-30. Used for portable AC label caution. Portable AC comparisons should check the current label and adjusted capacity context rather than relying only on the largest marketing BTU value.

  • ENERGY STAR Dehumidifiers

    Checked 2026-05-30. Used for dehumidifier capacity context: capacity is usually measured in pints per 24 hours and depends on both space size and existing conditions.

  • ENERGY STAR Dehumidifier Testing and Capacity

    Checked 2026-05-30. Used to distinguish pints/day moisture-removal capacity and efficiency testing from bucket volume or waterproofing claims.

  • Home Ventilating Institute: How Much Ventilation Do I Need?

    Checked 2026-05-30. Used for bathroom intermittent ventilation rules: under 100 square feet starts at 1 CFM per square foot with a 50 CFM minimum; larger bathrooms use fixture-based additions.

  • Home Ventilating Institute Bathroom Exhaust Fans

    Checked 2026-05-30. Used for bathroom exhaust fan context, including 50 CFM minimum classes, 1 CFM per square foot examples and delivered-airflow caveats.

  • Federal Register: Portable Air Conditioner Test Procedure

    Checked 2026-05-30. Used as source context for SACC, CEER, annual energy consumption and the distinction between portable AC adjusted capacity and a larger marketing BTU number.

  • EPA Brief Guide to Mold, Moisture, and Your Home

    Checked 2026-05-30. Used for the boundary that moisture-source control matters and dehumidifier sizing is not mold remediation, waterproofing or a health guarantee.

  • CFM and ACH Formula Reference

    Checked 2026-05-30. Used as formula-reference context for CFM = room volume × ACH ÷ 60 and ACH = CFM × 60 ÷ room volume.

  • ACCA Technical Manuals

    Checked 2026-05-30. Used to define the boundary between simplified room-level estimates and professional Manual J, Manual S and Manual D design.

  • EPA Mold and Indoor Air Guidance

    Checked 2026-05-30. Used for mold, water intrusion and indoor-air-quality disclaimers. Dehumidifier or fan sizing is not mold remediation or a health guarantee.