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HVAC Load Calculator
Free Manual J calculator with real ZIP-code design temps
Every free HVAC load calculator I could find makes you pick one of five climate regions, which can put you 20°F off your real design condition. This one resolves your ZIP code to published 99%/1% design temperatures and tells you how closely it matched. Eight inputs, whole-house heating and cooling BTU plus tonnage. No account, no email gate. Same engine as the iOS/Android app, checked by an automated parity test. Block load only, and it says so.
Hi Product Hunt. I'm Mike, I build HVAC field calculators as a one-person shop.
I built this because every free Manual J calculator on the web asks you to pick a climate region from a dropdown of four or five. Phoenix and Minneapolis are not the same load at the same square footage, and a 20°F miss on design temperature throws the whole number by about the same proportion. This one resolves your ZIP against published 99% winter / 1% summer design temperatures and tells you whether it matched a weather station, a reference city, or just the 3-digit prefix, so you know how much to trust it.
Honest scope: it's a whole-house block load from eight inputs. It won't do room-by-room, duct design, or Manual S equipment selection. Those live in the app, which runs the same engine (an automated test fails the build if the web and app numbers ever disagree).
No account, no email gate, nothing stored.
Question for anyone who's had an HVAC quote: did the contractor show you a load calculation, or just a tonnage?
“Free Manual J calculator with real ZIP-code design temps”
HVAC Load Calculator was submitted on Product Hunt and earned 11 upvotes and 2 comments, placing #71 on the daily leaderboard. Every free HVAC load calculator I could find makes you pick one of five climate regions, which can put you 20°F off your real design condition. This one resolves your ZIP code to published 99%/1% design temperatures and tells you how closely it matched. Eight inputs, whole-house heating and cooling BTU plus tonnage. No account, no email gate. Same engine as the iOS/Android app, checked by an automated parity test. Block load only, and it says so.
HVAC Load Calculator was featured in Android (57.7k followers), Productivity (663.6k followers), Home (170.4k followers) and Climate Tech (13.1k followers) on Product Hunt. Together, these topics include over 233.5k products, making this a competitive space to launch in.
Who hunted HVAC Load Calculator?
HVAC Load Calculator was hunted by Mike Watson. A “hunter” on Product Hunt is the community member who submits a product to the platform — uploading the images, the link, and tagging the makers behind it. Hunters typically write the first comment explaining why a product is worth attention, and their followers are notified the moment they post. Around 79% of featured launches on Product Hunt are self-hunted by their makers, but a well-known hunter still acts as a signal of quality to the rest of the community. See the full all-time top hunters leaderboard to discover who is shaping the Product Hunt ecosystem.
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Mike Watson