Cricket Chirp Thermometer
Estimate air temperature from cricket chirps with Dolbear's law. Count chirps for 15 seconds and add 40 — that's your temperature in Fahrenheit. Or run it in reverse to predict how fast crickets should be chirping.
Calculator
How Dolbear's law works
- Cold-blooded crickets chirp faster as the air warms. In 1897 Amos Dolbear published the linear relationship
T(°F) = 50 + (N − 40) / 4, where N is chirps per minute for the common field cricket. - Count chirps over a short interval and scale to per minute: chirps per minute = chirps × 60 / seconds. Example: 30 chirps in 15 seconds = 120 per minute → 50 + (120 − 40) / 4 = 70.0 °F.
- Handy shortcut for field crickets: count chirps for 15 seconds and add 40 — the result is the temperature in Fahrenheit (this is exactly Dolbear's law, since 4 × 15 s = 1 minute).
- Snowy tree crickets use
T(°F) = 50 + (N − 92) / 4.7— for example 144 chirps per minute → 50 + 52 / 4.7 ≈ 61.1 °F. The Celsius variant of Dolbear's law isT(°C) = 10 + (N − 40) / 7— 120 chirps per minute → 10 + 80 / 7 ≈ 21.4 °C. - Reverse mode: rearrange the formulas to predict chirp rate. At 70 °F, a field cricket chirps about 120 times per minute — 30 in 15 seconds, 40 in 20 seconds.
Results are estimates, typically accurate to about ±1–2 °F in calm conditions. Calibration is most reliable roughly between 50 °F and 90 °F; the calculator flags readings outside that band. Chirp rate also varies with cricket age, hunger, species and mating activity — this is nature, not a certified thermometer.
Frequently asked questions
What is Dolbear's law?
Dolbear's law is the 1897 observation by Amos Dolbear that a field cricket's chirp rate follows air temperature. The formula is T(F) = 50 + (N - 40) / 4, where N is chirps per minute. Worked example: 120 chirps per minute gives 50 + (120 - 40) / 4 = 70.0 degrees F, which is 21.1 degrees C. Because crickets are cold-blooded, they chirp faster as the air warms, and the relationship is nearly linear over a moderate range.
How do I count cricket chirps to measure temperature?
Pick one chirping cricket and count its chirps for 15 seconds. For a field cricket, add 40 to that count and the result is the temperature in Fahrenheit. Example: 30 chirps in 15 seconds equals 120 chirps per minute, and 30 + 40 = 70.0 degrees F. This shortcut is exactly Dolbear's law, because 4 times 15 seconds is one minute. Repeat the count two or three times and average for a steadier estimate.
Which formula should I use: field cricket or snowy tree cricket?
Most backyard chirping crickets are field crickets, so use T(F) = 50 + (N - 40) / 4. The snowy tree cricket (Oecanthus fultoni) chirps more slowly and follows T(F) = 50 + (N - 92) / 4.7. On that formula 92 chirps per minute means 50.0 degrees F, and 144 chirps per minute gives 50 + 52 / 4.7 = 61.1 degrees F. If you don't know the species, the field-cricket formula is the usual default.
Is there a Celsius version of Dolbear's law?
Yes. The Celsius variant is T(C) = 10 + (N - 40) / 7, with N again in chirps per minute. Example: 120 chirps per minute gives 10 + 80 / 7 = 21.4 degrees C. This calculator shows both units for every result, so you can also compute in Fahrenheit and read the converted Celsius value next to it.
How accurate is the cricket thermometer?
Treat it as an estimate, typically within about plus or minus 1 to 2 degrees Fahrenheit of a real thermometer in calm conditions. The calibration is most reliable roughly between 50 and 90 degrees F; the calculator flags readings outside that band. Chirp rate also shifts with the cricket's age, hunger, species and mating activity, so this is nature's party trick, not a replacement for a certified thermometer.
Can I go the other way: temperature to chirp rate?
Yes — flip to the reverse tab. Rearranging Dolbear's law gives N = 40 + 4 * (T(F) - 50). At 70 degrees F a field cricket chirps about 120 times per minute, which is 30 chirps in 15 seconds or 40 in 20 seconds. For the snowy tree cricket, N = 92 + 4.7 * (T(F) - 50): at 50 degrees F it chirps 92 times per minute.
Free tool by NRTechStudio