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Melon Meter
Thump a watermelon. Your phone tells you if it's sweet.
We all thump watermelons and nod like we heard something. It isn't folklore: ripe fruit is softer inside, so it rings lower — a gap of a few semitones, too small to hear. Thump 3 times, tap its rough size, get a 1-10. Optionally photograph the field spot and it reads that patch's exact colour and the rind's webbing. It measures ripeness, which correlates with sweetness — a phone, not a lab. Rate one after cutting and the scale re-fits to your melons. Free, no signup.
Hey Product Hunt 👋
It's peak watermelon season, and most of us are still picking them the same way: thump it, nod like we heard something, buy it anyway. I wanted to know what we're actually supposed to be listening for.
Turns out it's real physics. Ripe flesh is softer with bigger cavities inside, so the melon resonates lower. Unripe is dense and rings higher. The problem is the whole range is only a few semitones — too fine for our ears, easy for a microphone.
So Melon Meter listens for you:
Thump it three times. The mic catches each knock and picks out the melon's fundamental resonance.
Tap its rough size. That mass-normalises the reading, so a giant melon isn't penalised for being big.
Optionally, photograph the underside. Tap the pale field spot — the patch where it sat on the soil — and it reads that patch's exact colour, then scans the rest of the frame for the brown pollination webbing on the rind. Both nudge the score, and you see the arithmetic: thump, look, final.
Two calls that made it work:
Finding the right note. My first build used FFT peak-picking and kept locking onto the second harmonic, so every genuinely sweet melon scored a 1. Rebuilding around autocorrelation — which finds the fundamental rather than the loudest peak — was the difference between a novelty and something you'd trust.
Cutting a feature. I'd originally asked people to report the rind's webbing themselves. Then I realised I couldn't reliably tell webbing from the melon's natural green stripes — and if I couldn't, nobody could. That question was feeding noise into the score, so I deleted it and taught the app to read it from the photo instead, where brown scarring and green stripes sit far apart in hue even though they fool the eye.
Being straight about it: this measures ripeness, which correlates with sweetness — it's a phone, not a refractometer. It does get more personal over time though: rate four melons after you cut them and the scale re-fits to the fruit you actually buy.
Free, no signup, nothing to install. It runs entirely in your browser — your audio and photo never leave your phone.
Try it on your next melon and tell me how it did 🍉
finally an excuse to keep thumping melons at the store instead of pretending. tried it on a few in my backyard and the score lined up surprisingly well with the one i cut open.
love that it lets you rate after cutting so the scale actually learns your taste instead of pretending to know you from day one. the field spot + webbing combo is a clever touch too.
About Melon Meter on Product Hunt
“Thump a watermelon. Your phone tells you if it's sweet.”
Melon Meter was submitted on Product Hunt and earned 7 upvotes and 3 comments, placing #160 on the daily leaderboard. We all thump watermelons and nod like we heard something. It isn't folklore: ripe fruit is softer inside, so it rings lower — a gap of a few semitones, too small to hear. Thump 3 times, tap its rough size, get a 1-10. Optionally photograph the field spot and it reads that patch's exact colour and the rind's webbing. It measures ripeness, which correlates with sweetness — a phone, not a lab. Rate one after cutting and the scale re-fits to your melons. Free, no signup.
Melon Meter was featured in Web App (122.9k followers), Food & Drink (2.8k followers) and Physics (678 followers) on Product Hunt. Together, these topics include over 38.9k products, making this a competitive space to launch in.
Who hunted Melon Meter ?
Melon Meter was hunted by Yilan Dong. 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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Yilan Dong