Cricket Chirp Thermometer Calculator

What is Dolbear's Law?

Dolbear's Law is a formula first documented by physicist Amos Dolbear in 1897 in an article called "The Cricket as a Thermometer." He observed that the rate of cricket chirping is closely correlated with ambient temperature. As ectotherms (cold-blooded animals), crickets' metabolic rate -- and therefore their chirping rate -- increases with temperature.

The original formula published by Dolbear was:

Where T is temperature in degrees Fahrenheit and N is the number of chirps per minute. This can be simplified to the popular "count chirps in 14 seconds and add 40" rule.

Why Do Crickets Chirp?

Only male crickets chirp. They produce the sound through a process called stridulation -- rubbing the ridged edge of one wing (the "file") against the sharp edge of the other wing (the "scraper"). The chirping serves several purposes:

• Calling song: To attract females from a distance
• Courting song: A softer chirp used when a female is nearby
• Aggressive song: To warn other males to stay away from their territory
• Alarm chirp: A response to perceived threats

How Do Crickets Chirp?

The chirping mechanism involves specialized structures on the cricket's forewings:

1. The file is a vein with tiny teeth-like ridges on the underside of one wing
2. The scraper is a hardened edge on the upper surface of the other wing
3. When the cricket closes its wings, the scraper rubs across the file, creating vibrations
4. The wing acts as a resonator, amplifying the sound
5. The frequency of the chirp depends on the spacing of the teeth and the speed of wing movement

Why Does Temperature Affect Chirping Rate?

Crickets are ectothermic, meaning their body temperature matches their environment. Temperature affects their metabolism through:

• Enzyme activity: Chemical reactions in muscles speed up with higher temperature
• Muscle contraction rate: Warmer muscles contract faster
• Neural firing rate: Nerve signals travel faster at higher temperatures
• Energy availability: Metabolic processes produce energy more efficiently in warmth

This is an example of the Arrhenius equation in biology -- reaction rates approximately double with every 10°C increase in temperature.

The Cricket Chirps Temperature Formula

Common Field Cricket (Gryllus pennsylvanicus)

Simplified method: Count chirps in 14 seconds, add 40 = approximate °F

Snowy Tree Cricket (Oecanthus fultoni)

This species is sometimes called the "thermometer cricket" because its chirp rate correlates so closely with temperature.

Common Katydid

Converting to Celsius

How to Calibrate Your Cricket Thermometer

1. On a mild evening, go outside and listen for crickets
2. Use a stopwatch to count chirps for exactly 14 seconds (or 1 minute for greater accuracy)
3. Compare your calculated temperature with an actual thermometer
4. Note any consistent offset and adjust your calculations accordingly

Accuracy and Limitations

• Most accurate between 55°F and 100°F (13°C to 38°C)
• Below 55°F, crickets chirp very slowly or stop entirely
• Above 100°F, the relationship becomes less linear
• Different cricket species have different formulas
• Individual variation exists between crickets
• Humidity, wind, and other factors can affect chirping rate
• Accuracy is typically within ±1-2°F when conditions are ideal

Fun Facts About Crickets and Temperature

• A cricket chirping at 60 chirps per minute indicates approximately 55°F
• At 120 chirps per minute, the temperature is approximately 70°F
• Crickets cannot chirp below about 40°F -- they become too cold to move their wings
• The relationship was first scientifically studied in 1897 but was known informally long before

Tips to Stop Cricket Noise at Night

• Reduce moisture around your home (crickets love humidity)
• Seal cracks and gaps in walls, foundations, and around doors/windows
• Keep outdoor lights off (crickets are attracted to light)
• Mow grass short near the house
• Remove piles of debris, wood, or leaves near the foundation
• Use white noise to mask the sound if they're outside

Frequently Asked Questions