Cricket Chirp Thermometer (Dolbear’s law: temperature from chirps)

Understanding the cricket chirp thermometer — concept and principle

Crickets chirp faster when it is warm. In 1897 Amos Dolbear published a rule that turns the chirp rate of the snowy tree cricket into an air temperature. This calculator applies Dolbear's law to chirps you count.

Crickets chirp faster when warm; 128.6 chirps a minute points to about 72 °F (22 °C).

How it is calculated

Chirps per minute N = chirps counted × 60 ÷ counting seconds.
Dolbear's law: T(°F) = 50 + (N − 40) ÷ 4.
Equivalent shortcut: chirps in 14 seconds + 40 ≈ °F.
In Celsius: T(°C) = (T(°F) − 32) × 5 ÷ 9 ≈ 10 + (N − 40) ÷ 7.2.

The principle

Crickets are cold-blooded, so their body temperature follows the air. Chemical reactions in their muscles speed up as they warm, and so does the rhythm of the wing movements that make chirps. For the snowy tree cricket (Oecanthus fultoni), which chirps very regularly, the relationship is close to a straight line over the range where crickets are active, roughly 13–35 °C.

Worked example

Default inputs: 30 chirps counted in 14 seconds.

Chirps per minute = 30 × 60 ÷ 14 ≈ 128.6; chirps per 14 seconds = 30.
T(°F) = 50 + (128.6 − 40) ÷ 4 ≈ 72.1 °F (shortcut: 30 + 40 = 70 °F).
T(°C) = (72.1 − 32) × 5 ÷ 9 ≈ 22.3 °C.

Each point is the calculator re-run with only “Counting time (seconds)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Counting time (seconds)	Estimated temperature (°C)
3.5	75.9
7	40.2
10.5	28.3
14	22.3
17.5	18.7
21	16.3
28	13.4

How to read the result

The rule gives the temperature where the cricket sits, which may differ from a weather station reading. It works best for tree crickets; field crickets chirp less regularly and give rougher estimates. It is a fun way to practise counting and unit conversion, not a precise thermometer.

Common mistakes

Using the rule with the wrong cricket species.
Counting for too short a time, which adds error.
Applying it outside the crickets' active temperature range.
Forgetting that the result is in Fahrenheit before converting.

Keep in mind: This is a folk-science estimate for fun and education. Use a calibrated thermometer when accuracy matters.

Frequently asked questions

How do you tell temperature from cricket chirps?

Count chirps for 14 seconds and add 40 to get an approximate temperature in °F.

Does it work for all crickets?

It was derived for the snowy tree cricket; other species give rougher results.

Who discovered the cricket thermometer?

Amos Dolbear published the rule in 1897 in The American Naturalist.

Sources: Dolbear, A. E. (1897). The Cricket as a Thermometer. The American Naturalist, 31(371), 970–971. · Walker, T. J. (1962). Factors responsible for intraspecific variation in the calling songs of crickets. Evolution, 16(4).

Checked 9 Nov 2026. Standard formula: Dolbear’s law, A. E. Dolbear, “The cricket as a thermometer”, The American Naturalist 31:970–971 (1897) (original not opened in this session).

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