Cricket Chirp Temperature Calculator: Dolbear’s Law Thermometer
Turn cricket chirps into air temperature in °F and °C with Dolbear’s law, the snowy tree cricket and katydid formulas, or find the chirp rate expected at a temperature.
How it works
Chirps per minute N = chirps counted ÷ seconds × 60 · Dolbear’s law: T(°F) = 50 + (N − 40) ÷ 4, exactly the same as chirps in 15 s + 40 · Snowy tree cricket: T(°F) = 50 + (N − 92) ÷ 4.7 · Common true katydid: T(°F) = 60 + (N − 19) ÷ 3 · NOAA classroom fit: T(°F) = 0.714 × chirps in 15 s + 46.5 · T(°C) = (T(°F) − 32) × 5 ÷ 9
Crickets and katydids are cold-blooded, so the muscles that rub their wings together speed up as the air warms and slow down as it cools. In 1897 the physicist Amos Dolbear published a simple rule linking the chirp rate to the temperature, now called Dolbear’s law: take the chirps per minute, subtract 40, divide by 4 and add 50 to get degrees Fahrenheit. Because N ÷ 4 is the number of chirps in 15 seconds, the same rule becomes the familiar “count for 15 seconds and add 40”; the almanac version that counts for 14 seconds and adds 40 reads about 2 °F lower at typical summer rates. Dolbear did not name his insect, and later observers fitted their own formulas for the snowy tree cricket and the common true katydid, which chirp at different rates at the same temperature. NOAA’s education team also fitted a line to their own classroom counts, which you can pick for comparison. Enter how many chirps you counted and for how long. The calculator scales the count to chirps per minute, applies the formula you chose and shows the result in °F and °C, plus a table of what every formula says for the same count and a chart of temperature against chirp rate. Switch to “Chirps at a temperature” to run the formula backwards and see how fast a cricket should sing tonight. Count a single insect, on a calm evening, and treat the answer as an estimate of the air temperature where the cricket sits: crickets slow down and become irregular below about 55 °F and usually stop below about 50 °F. This is a nature activity, not a thermometer replacement; there is no closely related calculator on this site.
Worked example
You count 30 chirps in 15 seconds. The chirp rate is 30 ÷ 15 × 60 = 120 chirps per minute. Dolbear’s law gives T = 50 + (120 − 40) ÷ 4 = 70.0 °F, which is (70 − 32) × 5 ÷ 9 = 21.1 °C. For the same 120 chirps per minute the snowy tree cricket formula gives 56.0 °F, the katydid formula 93.7 °F and the NOAA classroom fit 67.9 °F, which shows why knowing the species matters.
Sources: NOAA: Can crickets tell the temperature? (Dolbear’s law and a classroom calibration) · Omni Calculator: Cricket chirp thermometer (species formulas, 60 chirps in 30 s example)
Frequently asked questions
How do you tell the temperature from cricket chirps?
Count the chirps of one cricket for 15 seconds and add 40 to get the temperature in °F. That is Dolbear’s law, T = 50 + (chirps per minute − 40) ÷ 4, rearranged. For example, 30 chirps in 15 seconds means about 70 °F. Some almanacs count for 14 seconds instead, which gives a reading about 2 °F lower.
How do you get Celsius from cricket chirps?
Work out the Fahrenheit value and convert it: °C = (°F − 32) × 5 ÷ 9. A quick field version of the same rule is to count chirps for 8 seconds and add 5, which lands within about a degree of Dolbear’s law across normal summer temperatures.
Is Dolbear’s law accurate?
It is a fair rule of thumb, usually within a few degrees on a warm evening, but each species and even each local population chirps at its own pace. Crickets sitting on warm walls or in the sun also sing faster than the air temperature suggests. Use the species formulas when you know what is singing.
Why do crickets chirp faster when it is warm?
Crickets are cold-blooded, so their body temperature follows the air. The chemical reactions that drive their wing muscles run faster in warmth, so each chirp takes less time and the chirp rate climbs.
At what temperature do crickets stop chirping?
Most stop below about 50 °F (10 °C), and between about 50 and 55 °F their chirping becomes slow and irregular. Very hot nights can also push the rate beyond the range the formulas were fitted for.
Related calculators
This calculator is for educational purposes. Double-check important results before acting on them.