Search “what size air conditioner do I need” and you’ll find plenty of calculators that spit out a single confident number, no caveats attached. That number is usually a rough rule of thumb dressed up as precision — and if you buy hardware based on it, you can end up with a unit that’s the wrong size for your room.
Our BTU calculator takes a different approach:
- Instant — adjust room size, ceiling height, insulation, sun exposure, and occupants, and the estimate updates as you type.
- Shareable — your inputs live in the link, so you can send a pre-filled estimate to whoever’s shopping for the unit with you.
- Honest — we tell you upfront that this is a simplified estimate, not a Manual J load calculation. It’s a great starting point for browsing; get a professional assessment before you actually buy.
- Private — the math runs in your browser. We never see your numbers.
Try it with your own room’s numbers, and if you write about home cooling or heating, the calculator is embeddable on your own site with one iframe.