The 5 Best Pool Thermometers

Before you take a dip, it’s a good idea to know just how warm — or cold — the water really is. After all, a higher temperature may demand more chlorine to eradicate germs that thrive in warm water, while a temperature that’s too cold can be hard on your body (and even unsafe). To ensure a safe and comfortable temperature, the best pool thermometers are made from shatter-proof materials and have easy-to-read temperature scales. Many have a buoyant design that allows them to float in your pool, while certain types can read your water’s temperature from above the surface.

There are two common types of floating pool thermometers: mercury and spirit. Mercury thermometers are more accurate in their readings, but since mercury is highly toxic, you’ll want to be sure it’s housed in a durable, shatter-resistant container. Spirit thermometers, although slightly less accurate, contain alcohol-based liquids, which are less harmful, so they may be the best option if you’ll be using the thermometer around kids, as the risk of breakage might increase. You can also opt for a digital thermometer that operates on solar power, but be advised that these tend to be less durable, so you may want to remove them from the pool after taking the temperature. Aside from floating options, a temperature-reading gun uses infrared technology to gauge the temperature from the water’s surface. These tend to be on the higher end of the price scale and require a separate 9-volt battery, but their LCD screens are much easier to read at a quick glance.

Then, there’s the overall aesthetic of your pool thermometer. Are you looking for something streamlined and simple? Go for a minimalist model that’ll blend right in with your pool. On the other hand, if you plan on frequently having kids in your pool — or just want something a little more whimsical — opt for a decorative thermometer shaped like a floating fish or whale.

I’ve rounded up the best swimming pool thermometers that will quickly and accurately read the temperature of your water. There’s even an option that not only acts as a thermometer, but as a chlorine diffuser as well. Happy swimming!

1. The Best Option For Most People

With a large display that lists both Fahrenheit and Celsius temperatures, this floating pool thermometer from eLander is a great no-frills model that gets the job done. The large, shatterproof tube is filled with mercury, which gives a highly accurate reading every single time. With large temperature markings up to 120 degrees Fahrenheit — or 50 degrees Celsius — this thermometer works in any pool or jacuzzi. An attached cord allows you to keep the unit tethered to the side of the pool. The basic all-white design doesn’t have any decoration, so it’s best for those who want an inconspicuous thermometer that gets the job done.

According to a reviewer: “This floating thermometer is exactly what I was looking for. It's very basic, but does what you'd expect. It seems pretty rugged, it floats, and it's easy enough to read. I haven't confirmed that the reading is calibrated perfectly, but it the reading on the thermometer feels about right to me. For the price, it's hard to not be pretty happy with this large floating thermometer. I would buy again.”

2. The Best Digital Pool Thermometer

As an alternative to a traditional model, this floating pool thermometer has angled digital displays on both sides that make it easy to read the numbers. The small solar panel on top keeps it powered up, and you can toggle between Fahrenheit and Celsius settings, although there’s no mention of what range of temperatures it measures. Reviewers have reported that — unlike with other options — it’s best to take this thermometer out of the pool and dry it off once it’s done taking the temperature, as the construction is not totally watertight. That being said, buyers are overall pleased with the accuracy and easy-to-read design.

According to a reviewer: “I was tired of straining my eyesight to read the small digits in my ‘old fashioned’ pool thermometer. Now I can see the numbers at a distance and I checked the accuracy against the usual thermometers and the Digital was not only accurate but fast to get to the new temperature.”

3. The Best Spirit-Based Thermometer For Kid-Friendly Pools

This floating spirit thermometer is filled with dyed kerosene — a less toxic alternative to a mercury — making it a great option for pools where kids (or rowdy adults) might be swimming. The durable, shatterproof tube displays the temperature up to 120 degrees Fahrenheit, or 50 degrees Celsius, and a cord allows you to tie the thermometer up so it doesn’t float away. Because it’s a spirit thermometer, the tube is smaller in size, making the numbers a bit harder to read, but the fun design more than makes up for that — the top of the thermometer has a playful cartoon fish, which doubles as a pool toy. There’s also an adorable whale option available, as well.

According to a reviewer: “Love this adorable goldfish thermometer! Accurate, easy to read, good price, and way better quality than expected! Not to mention he looks super cute floating around in my pool! No color fading at all like the other animal/fish themed pool thermometers I’ve bought in the past.”

4. A Non-Floating Option That’s Easy To Read

This temperature-reading gun is a high-tech alternative to a floating option, and the backlit LCD screen clearly displays the temperature in big numbers, making it much easier to read than a mercury or spirit thermometer. Using infrared technology, this device reads the surface temperature of your water from 14 inches away, and it can measure a wide range of temperatures, from -58 degrees to 1,382 degrees Fahrenheit (-50 degrees to 750 degrees Celsius). Plus, since you don’t have to fish the thermometer out of the water, it’s also the ideal choice for those who are unable to bend down to read the display. The only downside is that it’s not waterproof and you’ll have to change the 9-volt battery every now and then. But there are so many additional uses for this gadget — such as measuring the accuracy of your oven or refrigerator temperature — that it’s worth it.

According to a reviewer: “I use this all the time in the summer to check pool temperatures. It works great and is very accurate. Compared it to other thermometers and it was spot on. Battery has lasted all summer in my pool bag.”

5. A 2-In-1 Thermometer & Chlorine Diffuser

Not only does this thermometer from Aquatix Pro read your pool’s temperature, but it also diffuses chlorine into the water. The large, circular unit has a thermometer on the side that reads temperatures up to 120 degrees Fahrenheit, or 50 degrees Celsius, and the alcohol-based liquid inside the spirit thermometer is dyed blue for an easy read. There’s an internal chamber that can hold anywhere from five to seven 3-inch bromine tablets, releasing the chemical into your pool over time. A lockable cap on top ensures that the tablets stay inside, while an adjustable ring on the bottom allows you to control the amount of chlorine coming out. Although it’s not suitable for salt water pools, if you’re looking for space- and cost-efficiency, this option is a great choice.

According to a reviewer: “Love this product. Floats perfectly, stays upright - even after bumping into items or trying to disrupt it. Easy to open the top and add more chlorine, and never sinks or even attempts to sink. Temperature gauge is helpful as well as flow adjusters. Great value and exactly what I needed for our first pool.”