LoadSizer: HVAC Load & BTU

Size the AC right — get a room-by-room cooling and heating load estimate in under a minute, built on the ASHRAE CLTD/SCL method instead of a single "BTU per square foot" guess.

Built for installers doing a quick home survey, engineers who want a fast sanity check before a full Manual J, and homeowners who want more than a rule of thumb before buying an AC.

TWO MODES - Quick: floor area, ceiling height, room type, main sun-facing side, insulation level, occupants, top floor or not. Instant estimate. - Detailed: full room construction — exterior walls and windows by orientation (area, U-value, SHGC, shading), roof, ground-floor slab, occupants and activity, lighting, equipment, and outdoor air (ACH).

WHAT YOU GET - Sensible, latent and total cooling load (W, Btu/h, kW, ton) plus SHR, and a heating load for the coldest design day. - A horizontal breakdown by component: walls, windows (conduction and solar shown separately), roof, people, lighting, equipment, outdoor air. - A recommended commercial AC size (5,000-60,000 Btu/h) in Btu/h, ton and HP, rounded up to a size you can actually buy — plus a warning if it's oversized or the load per square foot looks off.

REAL CLIMATE DATA 35 cities across the Americas, Europe, the Middle East and Asia-Pacific, with outdoor design conditions sourced from ASHRAE Climatic Design Conditions — not one flat number for an entire country. Enter your own design climate for anywhere else.

WORKS THE WAY YOU DO - Fully offline. No account, no tracking, no ads. - °C/°F, m²/ft², m/ft, and W/Btu-h/kW/ton/HP, each set independently. - Multiple rooms per project, multiple projects, PDF export. - English, Spanish, Chinese, Portuguese, Japanese, Korean, Vietnamese and Thai.

Free for unlimited Quick estimates and one Detailed room. LoadSizer Pro (one-time purchase, no subscription) unlocks unlimited rooms/projects and PDF export.

LoadSizer uses a simplified ASHRAE Fundamentals 1997 CLTD/SCL/CLF method for fast sizing guidance — not a substitute for a full Manual J or ASHRAE RTS load calculation, and not certified or endorsed by ASHRAE or ACCA.

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