What is 湯温計（お風呂用）? (Bath Water Thermometer)
At just ¥110 (about $0.75), Daiso's Bath Water Thermometer punches way above its price tag — and it looks adorable doing it. Available in two designs — a waddling Penguin and a round Polar Bear — this floating thermometer is engineered to bob cheerfully on the surface of your bathwater while giving you an accurate temperature reading at a glance.
The body is made from polystyrene and glass, with a colored refined white kerosene solution inside as the thermometric liquid. The compact size — 7 cm × 15 cm × 0.7 cm — makes it light enough to float freely, yet large enough that the scale is genuinely readable. It measures a range of 0°C to 50°C, which comfortably covers the ideal baby bath temperature of 37–40°C. The rounded, corner-free silhouette is a thoughtful design choice: no sharp edges means it's safely in the water even when a little one is splashing around.
Daiso markets this primarily as a baby bath essential — and for good reason. New parents often find themselves nervously elbow-testing the water and hoping for the best. This thermometer removes the guesswork entirely. Drop it in, peek at the scale from above (no need to fish it out), and you'll know instantly whether the water is in the safe zone. Of course, adults who simply want their soak at a precise temperature will find this equally useful. One item, packaged individually, offered in two impossibly cute animal characters. Yes, this is ¥110.
How to Use It — Hack Ideas
Primary Use: Baby & Family Baths
Submerge the thermometer fully in the water once before reading — this ensures the liquid column adjusts accurately to the current temperature. Then just let it float. Check the reading from above whenever you want to confirm the bath is still in a comfortable range. No removal, no fuss.
Hack #1: Desktop Fish Tank / Aquarium Temperature Monitor
This one comes straight from real-world testing. The 0–50°C range maps almost perfectly to tropical freshwater fish requirements (typically 24–28°C). Rather than spending ¥500–¥1,000 on a dedicated aquarium thermometer, simply drop this penguin or polar bear into your fish tank. It floats, it reads accurately, and — let's be honest — a polar bear floating in a tank is a conversation starter. Just make sure the glass and kerosene liquid are fully sealed before use (they are, as factory-sealed).
Hack #2: Home Brewing & Fermentation Aid
Making yogurt, amazake, or sourdough starter at home? Temperature control is critical during fermentation. This thermometer floats in a pot or bowl of warm water used as a bain-marie, letting you monitor heat levels without a dedicated kitchen probe thermometer. It won't give you decimal precision, but for home fermentation it's more than adequate — and cleanup is a breeze.
Reviews & Verdict
User sentiment around this product is overwhelmingly warm (pun intended). Reviewers consistently highlight three things: how easy it is to read without removing it from the water, how the floating design feels intuitive and stress-free, and — perhaps most frequently mentioned — how genuinely cute these little animals look bobbing around in the tub. Comments like "I just want to put it in water immediately" and "this level of simplicity is exactly what I needed" are typical of the feedback.
Parents of infants are the most enthusiastic audience. The rounded body earns particular praise for being baby-safe, and multiple reviewers note that the 0–50°C range is more than sufficient for all real-world household needs. The polar bear variant, with its clear white body and red liquid scale, scores especially well for readability.
A few caveats worth noting: the thermometer is glass-bodied, so handle with care around tile floors and ceramic tubs. The colored liquid is refined white kerosene — non-toxic in sealed form but not something to expose to open air intentionally. And as a floating design, it drifts freely, so in a large tub it may wander to a corner. Minor issues for a product at this price point.
Bottom line: for new parents, pet owners, home fermenters, or anyone who wants their bath at exactly the right temperature — this is a no-brainer purchase that happens to be adorable.
Value Score: 88/100
Price-to-quality is exceptional for a glass thermometer with a 0–50°C range at ¥110, and the dual-design character appeal adds genuine delight to a purely functional item. Hack potential beyond the bathtub — aquariums, fermentation, hot water monitoring — pushes this firmly into "great value" territory, held just short of gem status only by its glass fragility and free-floating drift.
**Value Score: 88/100** — Great value, worth every yen. --- *All product images: Source: daisonet.com*
