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Compost Thermometer: The Ultimate Guide

Compost thermometers are specially built to accurately measure the heat emanating from the compost pile, which comes in handy when tracking the composting process. This is crucial in determining whether the compost pile is decomposing as expected or it needs a boosted. This guide will take you through the various considerations you need to make while getting a compost thermometer, how to use it, and how to clean and maintain your compost thermometers.

What Is A Compost Thermometer?

A compost thermometer is a piece of rugged heat measuring equipment that operates just like a standard thermometer. It’s equipped with a long probe that penetrates deep into the compost pile to get accurate temperature readings. A compost thermometer has a wide temperature range, usually from 0 to 220 degrees F. The dial is also sealed in to prevent moisture from leaking in when exposed to moisture, which is bound to happen when dealing with multiple batches of compost. Further reading material: link.

Why Use A Compost Thermometer?

1. Know When To Turn The Pile Of Compost

After initially piling up the compost, you should allow it to decompose at least for two weeks so that the interior can heat up to around 140 degrees Fahrenheit. When the temperature drops to below 100 degrees F, you should turn the pile of compost so as to decompose the remaining organic matter evenly. The temperature will gradually rise back up, and the cycle is repeated again when the temperature reading from the compost thermometer indicates a drop.

2. Know When The Compost Is Ready

Eventually, after a few rounds of turning the compost, the temperature reading from the compost thermometer will gradually indicate a fall towards 80 degrees F, indicating that the compost is mature and fully decomposed. The mature compost should then be spread out into smaller piles or rows to allow air to circulate and exposure to the sunlight, which further eliminates any remaining pathogens.

3. To Identify The Decomposition Rate

You can use a compost thermometer to track the changes in the temperature of the compost, which indicates whether the microbial activity has picked up or is slowing down. Having such information, you can then decide to either apply a compost booster or turn the compost.  The end result is a natural mix of essential nutrients for your plants and increased production. Further reading material: link.

Considerations When Buying A Compost Thermometer

1. The Length Of The Probe

The length of the compost thermometer’s probe will determine how accurate your temperature readings will be. Short probes are less likely to poke all the way through to the center of the compost, and thus the readings will be much lower. However, it's important to remember that long thermometer probes cost more, and this can just be solved by starting out with smaller sized compost piles.

2. How Easy It Is To Read

Having easy readability will eliminate the possibility of taking the wrong temperature measurements. It's recommended to go for compost temperatures with sealed temperature gauges, which are much clearer to read. The dial should also be luminescent to further enhance the readings even in low light conditions.

3. The Quality Of Materials Used

The quality of materials used to manufacture the compost thermometer will significantly influence its longevity. Always go for heavy-built compost thermometers with stainless steel casings, which are not only corrosion proof but also strong enough to withstand regular drops while working on the compost. The temperature gauge should also be covered with a firmly fixed piece of glass or acrylic that's easy to see through but also strong enough to withstand cracking when dropped.

4. The Time It Takes To Get A Reading

The time it takes to get a consistent reading from a compost thermometer will depend on the mechanisms being used to detect heat. Whereby mercury-based thermometers, take up to 2 minutes to get a steady and consistent reading while alcohol-based ones take up to 4 minutes to get consistent readings. Digital compost thermometers take less time to get accurate readings compared to conventional ones. Further reading material: link.

How To Use & Read A Compost Thermometer

  1. Gently take out the compost thermometer from its storage case and slowly poke the probe into the compost, preferably at the top straight down to the center of the pile. 
  2. Allow the temperature to rise accordingly until the temperature dial indicates a consistent and stable reading, which you should note down. A temperature reading of around 120 to 140 degrees F indicates that the composting process is going on optimally. On the other hand, a reading of below 100 degrees means that the compost needs to be turned.
  3. Take the compost thermometer out of the compost and clean it thoroughly with soapy water before wiping it dry and storing it in its case for future use.

DIY Compost Thermometer

Tools Required

  • pliers
  • hacksaw or any thin blade hand saw

Equipment Required

  • a small screw
  • a small dry fallen branch
  • An old fish tank thermometer. Alternatively, you can get one from Amazon.


  1. Construct a firm mount for the probe using the fallen branch or a piece of wood.
  2. Run the cable around the wooden mount from the probe to the fish tank thermometer.
  3. Mount the thermometer display onto the contraption and secure it in place with galvanized strapping. 
  4. Gently push the probe end of the firm mount into the compost until it's firmly in the center of the compost. Wait for around 3 minutes or until the thermometer gives a consistent reading for 1 minute and record the temperature. 

Further reading material:

Top 5 Compost Thermometer [Include For A Variety Of Scenarios]

1. Greenco Gardening

Where To Buy:


The Greenco gardening compost thermometer features a 20 inch long stem that's solidly built and joined to the dial via a welded bolt. This thermometer can accurately measure temperature with the 40 to 180 degrees F range. The dial is pc coated and enclosed with a high-quality lens, which further enhances the visibility of the dial. The seal is watertight, which prevents fogging and moisture accumulation. 

Price: $61.98


  • Features a reinforced stainless steel build, which is corrosion-proof 
  • Clear, accurate, and color-coded for faster observation.


  • Some of the customers questioned the quality of the hematic seal and water resistance.

2. Reotemp

Where To Buy:


For over the last 20 years, Reotemp has been producing high-quality thermometers, including its latest 20-inch compost thermometer. The quarter-inch thick stem is built to last for years and will easily pierce through any compost pile. The dial is also hermetically sealed to prevent fogging and has three temperature regions, which indicate the activity of your compost accordingly. 

Price: $18.85


  • They are hermetically sealed to prevent fogging when left in the garden overnight.
  • Relatively more affordable compared to other similar thermometers. 


  • This compost thermometer only has a Fahrenheit scale and lacks a Celsius scale on the dial.

3. Cate’s Garden Store Compost Thermometer

Where To Buy:


Cate’s garden compost thermometer features a 2-inch wide gauge and a 20 9nch long stainless-steel probe to get precise temperature measurements. This compost thermometer can measure temperature changes within the range of 40 to 180 °F with a 2 degrees difference between each annotation. The dial is also color-coded into three major phases for quick readings. The dial is enclosed with a pc-coated lens that serves to magnify the readings while also preventing fogging.


  • High-quality 304-grade stainless steel that's not only durable but also rust resistance.
  • It takes as little as 30 seconds to get accurate readings using this compost thermometer. 


  • Some reviewers questioned the lack of information regarding where the product is manufactured for quality assurance purposes.

4. Thermopro

Where To Buy:


Thermopro digital T17 thermometer features dual probes and a multi-purpose design that comes in handy when constructing a DIY compost thermometer set up. Simply hook the two probes to a branch, which can then be implanted into the compost pile and take readings. This digital thermometer can sense temperature changes from 14˚F to 572˚F. 

Price: $26.99


  • Dual probe setup for the most precise and consistent temperature readings
  • Comes with a 40-inch long stainless steel mesh cable


  • You will have to change out the triple-A batteries as they are not rechargeable.

5. Reotemp 36 inch Stem Compost Thermometer

Where To Buy:


Reotemp is offering its top of the line compost thermometer with a 36-inch long temperature probe that will be enough to get precise temperatures from the center of the compost pile. This compost thermometer has a rugged stainless steel construction with a welded bolt attaching the dial to the probe. The 2.5-inch wide dial is also hermetically sealed to prevent fogging.

Price: $74.99


  • The dial features three temperature zones to indicate the compost activity.
  • Ships with a pdf guide on how to use and maintain the product.


  • The compost thermometer is rather pricey compared to other similar models.


Common Questions

Do You Need A Compost Thermometer?

Yes, you need a compost thermometer to keep track of the interior temperature of your compost piles and know when they are ready.

How Do I Know If My Compost Is Composting?

A constant increase in temperature indicates that the compost is decomposing as expected; this release of heat results in moisture evaporation, which can be seen in the form of steam rising from the surface of the compost.

How Does A Compost Turner Work?

A compost turner works by regularly turning the compost to mix it in mechanically, which allows the bacteria and fungi cultures to feed on the organic matter and populate the entire batch of compost.

How Often Should I Turn My Compost?

It's recommended to turn the compost every two2 days or at least twice per week.

How Do You Make A Compost Pile?

To make a compost pile, you will need to shred the organic plant matter before mixing it with the farmyard manure in layers until they form a sizable pile. 

Are Maggots Good For Compost?

Yes, maggots combine the compost and bore tiny holes through it, which increases the aeration rate in the compost. Maggots also feed on organic matter and leave behind nutrients, which are eventually absorbed by the plants.

Should There Be Flies In My Compost?

Flies are naturally attracted to compost piles, which are a source of food for the flies. 

Is Urine Good For Compost?

Yes, urine increases the nitrogen content in compost, which is excellent for vegetative plants like vegetables.

Can You Use Shredded Paper In Compost?

Yes, you can add shredded unbleached paper to compost; however, avoid colored and glossy print paper as it may contain harmful heavy metals that are harmful.

Can You Put Moldy Fruit In Compost?

Yes, moldy fruit will completely rot and release additional nutrients into the compost.

Does Compost Turn Into Soil?

Over time compost gets mixed with other secondary particles and becomes almost like the topsoil layer.

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