5 Best Compost Thermometers - Super Accurate Tools To Measure Your Compost Temperature

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by Max - last update on July 9, 2019, 2:08 am
Compost Thermometer

Making your own compost is a great way to repurpose your garden and household waste, as well as creating an organic fertilizer to give your soil and plants a nutrient boost. But are you struggling to know when the best time to turn your compost pile is?

The secret to perfect compost is getting it to the right temperature before you turn it. Heat activates the microbes within the compost, and turning the heap at the key time will encourage a faster production and higher quality compost. A compost thermometer will give you the confidence to know exactly when to turn your compost, but there are so many models available, it can be difficult to know which is the right compost thermometer for you.

Buyers Guide

If you are new to composting and eager to learn how to get the best out of your household and garden waste, then a compost thermometer will be your best friend to guide you through his journey. Even as an experienced composter, you might be surprised to find out how much impact a compost thermometer could have on your composting process.

A compost thermometer simply tells you the temperature of the compost at the center of your pile, but this information is key in knowing when to turn your pile when to add more material to the pile, when to add water to it, and when the compost is finished. Knowing these things take the guesswork out of producing compost and typically result in a better quality compost made in a quicker time frame.

What Makes the Compost Heat Up?

Compost typically starts to heat up within a few days from the batch being created. This heat is generated from microbes within the waste material as they breathe, multiply, eat, and excrete. These microbes are vital to breakdown the rotting material and turn it into nutritious compost. The heat is indicative that your compost is starting to work.

What Does the Temperature Tell Us?

Compost goes through three stages before it reaches maturity. First off is the mesophilic stage; you will know this stage is happening when the temperature on your thermometer reads between 68° F to 104° F.

At this point you should turn your compost so that it can progress to the second stage, which is the thermophilic stage; this is indicated by a temperature of 105° F to 150° F. When temperatures reach this level, you can turn the compost pile again so that it can progress to the third and final stage, the maturation stage.

You will know when this stage has been reached because it will not heat up any further, even with additional turning. At this point, your compost has matured and is ready to use.

When you are searching for a compost thermometer, there are some key features you need to look out for. These are:

Measuring Units

Residents of the US will most likely want their compost thermometer in Fahrenheit, while UK residents typically recognize temperatures measured in Celsius. Take note of the measuring unit on the compost thermometer you purchase to ensure that you understand the temperature measures taken. Some thermometers have dual temperature scales in which both Fahrenheit and Celsius are shown.

 

Temp Range

Your thermometer will need a wide temperature range able to detect the correct temperature of your compost pile. A thermometer with a small temperature scale may give you incorrect readings if your compost pile heats up to a higher temperature than the thermometer can read.

 

Probe Size

This is one of the most important elements when selecting your ideal compost thermometer, and it will be determined by the size of your compost pile. If you are composting in a tumbler or small bin, then your probe will not need to be very long to reach the center of the compost heap where the temperature reaches its highest point.

A large compost pile will need a longer probe to reach its center. A 20-inch probe is typically more than long enough to suit most backyard compost piles, but if you compost on an industrial level, then there are compost thermometers available even longer than this.

 

Construction Quality

This is another key aspect you will want to look out for. Low-quality compost thermometers have probes made from substandard metal which can bend or break when inserted into a dense compost pile. Stainless steel is the ideal material for a compost thermometer because it should be strong enough to withstand pressure, which causes bending, and it will also be resistant to rust.

In terms of size, the thicker the diameter of the stem, the better. A chunky stem will obviously be stronger and much less likely to bend or break than a thin one. If quality is important to you, then find a compost thermometer with a thick stem in a sturdy material. Otherwise, it is likely you will have to replace a lower quality compost thermometer every few seasons because they need to withstand a fair amount of abuse, and if they are not robust, they will not stand the test of time.

 

Ease of Use

Compost thermometers, in general, are incredibly easy to use; you simply prod the stem into the compost and read the dial. However, some are much easier to read than others. Look for a large dial, which will be easy to read from a short distance, preventing you from having to get too close to the pile.

Color-coded zones are present on most good thermometers, which indicate what each temperature range represents. These are usually ‘warm,’ ‘active,’ and ‘hot.’ Being able to ascertain which zone your compost is in from the color coding is great because you won't have to remember what each temperature range correlates to. If your eyes aren’t what they used to be or you struggle to see small print, the color coding on a large dial will make using your thermometer much easier and much more convenient.

 

Waterproof

It is vital that the dial of your compost thermometer is resistant to moisture, as otherwise, you will find that the dial becomes fogged up and impossible to read. Good thermometers will be hermetically sealed, which protects the dial against moisture seeping in and causing any damage. Look for hermetic sealing when you are shopping for a compost thermometer, though pay attention to reviews, as not all hermetically sealed dials were created equal.

Some users find that certain compost thermometers get fogged up even when the dial is claimed to have been hermetically sealed. This is an especially important feature to look out for, because if your dial becomes fogged, and you can’t see the temperature reading, then the whole device is utterly useless.

 

Top 5 Compost Thermometers Reviewed

 

 

Product Comparison

Each of these compost thermometers works well to accurately display the temperature of your compost heap, giving you the information you need to understand when to turn or add to your heap, or how to know when it is finished. However, there are variations between each thermometer which might make them better suited to your depending on your preferences.

If you are looking for an extra-long stem on your thermometer to reach the center or extra-large or industrial sized compost heaps, then undoubtedly, the Reotemp Heavy Duty Compost thermometer is the one for you, with a stem measurement of 35 inches, almost double that of its competitors. However, this added length does come at an added price, costing almost $100 more than the best 20-inch models on the market.

If an easy-to-read dial is for you, then the Greenco Gardening Compost Soil Thermometer is your best friend. It features a brilliantly designed face allowing you to see the temperature of your pile from just a quick glance.

One of the main problems with compost thermometers is the way that the dial can fog up from moisture. A fogged-up dial is impossible to use as it prevents you from seeing the temperature reading, and the whole device becomes completely useless. All of these thermometers have hermetically sealed dials, which should prevent this occurring, but in reality, some of them proved to be more resistant to moisture than others. If you are concerned about the possibility of a screen becoming fogged up, either of the Reotemp thermometers would be your best purchase, as users of these thermometers did not experience any fogging.

 

Top Pick

REOTEMP Heavy Duty Compost Thermometer

REOTEMP Heavy Duty Compost Thermometer

This industrial grade compost thermometer from Reotemp has been designed with serious composters in mind. It benefits from a stainless steel body, which won’t rust over time, and a sturdy 36-inch stem, which will reach the center of even extra-large compost heaps to give you an accurate temperature reading.

With a diameter of 5/16-inch, you can confidently insert this thermometer into dense compost piles without running the risk of snapping the pole or causing it to bend. It has a large dial making for easy reading, with dual temperature scales in a wide range; from 0 to 200° F & -10 to 90° C. The dial is also hermetically sealed, preventing it from fogging up or falling victim to water damage.

User reviews of this product are overwhelmingly positive. They are impressed with the solid construction of the thermometer and believe it will last a lifetime, being able to be passed on to generations to come. Users suggest that this thermometer is ideal for industrial composting sites or anyone who appreciates having the highest quality tool available. Users comment that the tool is fairly expensive at just under $120, but this does represent good value for money as it is so rugged it should never need to be replaced, whereas less expensive models may only have a lifespan of a few years or even just a few months.

Pros
  • Heavy-duty
  • Well-thought-out design
  • Chunky, long stem
  • Large face
  • Won’t rust or fog
  • Dual temperature scale
  • Can be recalibrated
Cons
  • High price
  • No color coded temperature zones

 

Best Value

REOTEMP Backyard Compost Thermometer

REOTEMP Backyard Compost Thermometer

This thermometer features a 20-inch long stem with a ¼-inch thickness, making it sturdy enough to prod into your compost pile without bending or breaking. It’s made from stainless steel, which further adds to its rugged durability. It has a reasonably sized face at around 2 inches, and the dial is color coded to show when your compost has reached the ‘steady, ‘active,’ or ‘hot’ zones. This is incredibly helpful as it allows you to instantly recognize what stage your compost is at, rather than remembering which temperature correlates to which zone.

It has a reinforced construction to prevent the dial separating from the stem, along with a hermetically sealed dial to prevent fogging up. The other advantage of this is that you can leave the thermometer in the compost pile overnight without the dial incurring any water damage. You have the option of purchasing the thermometer in either Fahrenheit or Celsius versions, which will be fine for most people, though it might have been an improvement to show both temperature measurements on one dial.

Users of this compost thermometer rate it highly for use in the backyard. Twenty inches is a reasonable length for most backyard composters, though more serious composters might need a longer stem. Users are impressed with how durable the thermometer seems compared with other similar priced compost thermometers, expectant that it will last several years. Users also noted that the packaging contained no plastic, making it environmentally friendly.

Pros
  • Sturdy construction
  • Hermetically sealed dial
  • Chunky, stainless steel stem
  • Color-coded temperature range
  • Reasonably priced
Cons
  • Probe too short for larger piles

 

Cate's Garden Compost Thermometer

Cate's Garden Compost Thermometer

With a 20 inch probe constructed of rust-resistant stainless steel, this compost thermometer is designed to be rugged and long-lasting. The stems diameter is 3/16-inch, making it less susceptible to bending or breakage than less robust thermometers. The dial is hermetically sealed to prevent fogging or water damage, and the face shows a temperature range of 40° F to 180° F, with a Celsius conversion.

Color-coded zones are shown on the dial to help you quickly ascertain which zone your compost is in and which action you need to take as a result. A temperature read takes just 30 seconds, with the sensitive portion being on the tip of the probe. The product features a money-back guarantee to ensure you are happy with the purchase, and an extended 5-year warranty.

Users of this product are predominantly very happy with it. They are impressed with how sturdy it is, how easy it is to use, and how much it improves their compost-making process. Some users did experience condensation on the inside of the clear plastic dial, which suggests that this product is not resistant to water damage as it claims to be, and should not be left outside to maintain the best condition. Some users also found that this product broke after a few months of use, though many others found that it was lasting well.

Pros
  • Sturdy construction
  • Color-coded temperature zones
  • Dual-temperature display
  • 5-year warranty
  • Reasonably priced
Cons
  • Susceptible to dial fogging
  • Stem not long enough for larger piles

 

Greenco Gardening Compost Soil Thermometer

Greenco Gardening Compost Soil Thermometer

The outstanding feature of this compost thermometer is its large dial, which features clearly displayed temperature zones. It makes it ideal for judging your composts state with just a quick glance or would be perfect for anybody who struggles to see small writing. The compost has a 20-inch stem made from stainless steel, at a diameter of ⅕-inxh. This means the probe should be able to withstand being inserted into dense compost piles without running the risk of bending or breakage.

The dial is hermetically sealed to protect against moisture damage, and the product comes with a lifetime guarantee. At around the $20 mark, it is reasonably priced and comparable to other similar compost thermometers in this price range.

Users of this product offer mixed reviews. Some believe it is the best garden gadget they have purchased, while others have been disappointed with its longevity or lack thereof. While all users of this product agreed that it worked excellently at first, for some, it let them down after a few weeks or months use, with the dial becoming fogged up. If you can’t see the temperature reading due to condensation or fogging, then this renders the thermometer completely useless, so it is vital that the hermetically sealed dial prevents water damage as it is supposed to.

The main thing that users of this product liked was the easy to read dial with color coding. It makes the thermometer easy to use and more convenient than having to squint at the dial to read it or fetch a pair of glasses.

Pros
  • Stainless steel construction
  • Large, clear display
  • Color-coded dial
  • Robust design
  • Reasonably priced
  • Lifetime warranty
Cons
  • The dial might fog up

 

Ecocycle Backyard Compost Thermometer

Ecocycle Backyard Compost Thermometer

This compost thermometer has a 20-inch stem with a ⅕-inch diameter made from stainless steel, making it long enough to reach to the center of most average sized compost heaps without bending or breaking. It has a 2-inch display dial with a temperature range of 40° F to 180° F, with color-coded zones labeled ‘warm,’ ‘active’ and ‘hot.’

The dial only displays temperature in Fahrenheit with no conversion to Celsius, which may be a problem for some people. With a hermetically sealed dial, Ecocycle claims that this product won’t fog up and is suitable to be left in the compost heap overnight.

User reviews of this product vary dramatically. Some users are happy with the product and the learning journey the thermometer has helped them to go on to create better compost. However, some people have been unimpressed with the product for two main reasons. Some users found that the dial did fog up when left outside for just one night, which could mean that the product they received was faulty and not hermetically sealed correctly or that the product is simply not as high quality as it claims to be.

Some users also experienced bending and breaking of the stem, either during use or becoming bent during shipping. This suggests that the stem is not necessarily as robust as it claims to be.

Pros
  • Reasonably priced
  • Hermetically sealed dial
  • Color-coded display
Cons
  • The dial may fog up
  • The stem may experience bending
  • Dial display only in Fahrenheit

Conclusion

The standout product from these top compost thermometers is the REOTEMP Backyard Compost Thermometer. It is made by a renowned manufacturer of compost equipment with over 20 years of experience and specialty composting knowledge and has all of the features that most people who compost for a hobby will want or need.

It is incredibly sturdy with an easy-to-read face, and probably most importantly, a hermetically sealed dial that really works. Its competitors in a similar price bracket who claim that their thermometers are hermetically sealed have experienced some reports from users who say that the dials still fog up, whereas users of the REOTEMP Backyard Compost Thermometer have nothing but praise.

For a little over $20, this compost thermometer offers outstanding quality and should stand the test of time. The only other thermometer that outperforms this one is the REOTEMP Heavy Duty Compost Thermometer, but at over $120, it is likely not worth the expense for most backyard composters.

If money is no object to you, then the REOTEMP Heavy Duty Compost Thermometer is an outstanding piece of compost equipment, and if you can stomach paying this price for a thermometer, then you will no doubt be over the moon with your purchase.

5 Best Compost Thermometers - Super Accurate Tools To Measure Your Compost Temperature

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