Cricket Chirp Temperature Calculator

You can tell the temperature by the song of crickets. By counting how fast they are singing and doing a simple calculation you get a value that is usually equivalent to what's on a thermometer.

Humans have known since the 1890s that there is a relationship between the frequency of song and temperature. This holds true best for the snowy tree cricket, which has earned it the nickname "thermometer cricket". By entering the number of calls and selecting the species, one can obtain the temperature in Fahrenheit, Celsius or Kelvin.

What is Dolbear's Law?

In 1897, physicist Amos Dolbear published a law called "The Cricket as Thermometer", which established a relationship between temperature and the rate at which crickets chirp. The warmer it is, the faster they chirp, and this relationship is stable enough to calculate the temperature from backwards.

The reason for this is their biological properties. As they are cold-blooded animals, the temperature of their bodies gradually approaches that of the ambient air.

To sing they need to contract their muscles quickly and this contraction depends on chemical reactions. Chemical reactions happen more quickly at higher temperatures and slower at lower temperatures. A cricket singing on a cold evening will be muffled, whereas the same cricket will sing loudly on a warm evening.

This is how this calculation tool works:

Find a cricket chirping at a constant rate. Use a stopwatch or smartphone to measure 15 seconds and count the number of chirps during that time. Leave the temperature field blank.

If you can identify the type of cricket you heard, please select that species. Field crickets are most common but tree values are more accurate. The calculator will automatically convert your count of crickets per 15 seconds into a rate per minute so you do not need to calculate this yourself.

You can also do the conversion in the opposite direction. If you fill in the temperature field and leave the chirps field blank, it will show you the expected frequency of chirps.

Understanding of formula.

The original law that Dolbear measured with snowy tree crickets is a straight line.

where T_F is the temperature in Fahrenheit and N is the number of chirps per minute. For example, if you counted 14 chirps and timed it for 15 seconds, that would be a frequency of 56 chirps per minute.

A simple method that many remember is to count the number of chirps in 15 seconds and then add 40.

As field crickets chirp slightly faster at the same temperature, this tool uses a slightly flattened slope.

This is the method where you "count the number of chirps in 14 seconds and add 40." If you change the temperature scale, then the calculator will usually convert from Fahrenheit to Celsius.

The table below shows the chirp frequency predicted by each expression for various temperature ranges.

The calculations for the Example #2 are as follows:

There are some limitations to keep in mind. Crickets don't chirp below about 50 °F (10 °C), and the formula works best between about 55 and 100 °F (13 and 38 °C). The frequency of field crickets varies with age and mating success, which makes them a less reliable data source. In contrast, tree crickets follow the rules consistently.

What is a cricket thermometer good for?

It's true that it can be a small novelty to bring out at parties, but there are other benefits. Hikers and campers can check the temperature without having to carry around a thermometer, and teachers use it to teach their students about biology, physics, and basic math.

Citizen scientists record the number of calls to track cricket populations and seasonal changes. Gardeners listen for chirps on cool evenings to determine the danger of frost. And in summer it's a good way to spark conversation.

Tips for accurate measurements:

Count individual crickets rather than the whole group. Count for as long as possible up to a maximum of 15 seconds. If possible count two or three times and average them out.

The light green snowy tree crickets live on trees and shrubs and give more accurate readings than the dark brown field crickets that live on the ground. Do not take measurements within half an hour after sunset as the temperature falls too quickly during this time to make an accurate determination.