# 🍺 Top-down Brew: Specific gravity temperature correction

Purpose: To adjust hydrometer specific gravity readings based on temperature.

Specific gravity
Temperature

US units (fahrenheit) Metric units (celsius)

Results: *** Waiting for results ***

## Discussion

Most hydrometers are calibrated to read 1.000 at 60F (15C) in pure water. Hydrometers indirectly measure the presence of dissolved sugar because this increases the density of the water (viscosity) and makes the hydrometer float higher. Temperature is another variable that will affect water density. Temperatures higher than 60F, for example, will thin the density of the water and cause the measurements to be too low.

This calculator corrects for hydrometer samples that deviatiate from 59F. The correction formula is from Lyons (1992), who used the following formula to fit data from the Handbook of Chemistry and Physics (CRC): 1.313454 - 0.132674*T + 2.057793e-3*T2 - 2.627634e-6*T3. The symbol "T" stands for temperature in degrees Fahrenheit.

## References

Lyons, C. (1992). Hydrometer temperature corrections. Home Brew Digest #963

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