Gravity Correction Calculator - Brewing, Bouguer & Mass

Correct brewing hydrometer SG, calculate free-air and Bouguer anomalies, or adjust indicated mass for local gravity and air buoyancy with visible terms.

Brewing Temperature Correction Formula

The following formula approximates a hydrometer temperature correction in Specific Gravity (SG), assuming water-like liquid expansion and neglecting hydrometer glass expansion. This calculator accepts and returns SG; it does not convert °Plato.

SG corr = SGₘₑₐₛ \times (ρ w (T ref)) / (ρ w (Tₘₑₐₛ))

Variables:

SG_corr is the temperature-corrected specific gravity (dimensionless)
SG_meas is the measured specific gravity at the sample temperature (dimensionless)
ρ_w(T) is the density of pure water at temperature T (kg/m³)
T_meas is the sample temperature (°C)
T_ref is the instrument calibration/reference temperature (°C)

Note: hydrometer temperature correction can be instrument-specific (and may include glass expansion and wort thermal expansion). For best accuracy, use the manufacturer’s correction table. This calculator uses a water-density approximation over a numerical temperature range of 0–100°C. That range does not establish hydrometer accuracy; prefer measurement near calibration temperature and the manufacturer’s instrument/liquid correction table.

What is Gravity Correction?

“Gravity correction” can mean different things depending on context. In brewing, it usually means adjusting a hydrometer gravity reading for temperature differences from the hydrometer’s calibration temperature (commonly 20°C or 60°F). In geophysics, gravity corrections are applied to measured gravitational acceleration to help compute anomalies (such as free-air and Bouguer anomalies). In mass metrology, instrument calibration determines whether a local-gravity correction is needed. A locally calibrated comparison cancels gravity, while the modeled force-responsive scale calibrated against reference weights at standard gravity requires the stated g0/local-gravity factor. Both mass paths assume identical air density during calibration and use.

How to Calculate Corrected Gravity?

The following steps outline how to calculate a brewing temperature-corrected gravity reading.

Measure the hydrometer reading as Specific Gravity (SG).
Record the sample temperature (T_meas) and the hydrometer’s calibration/reference temperature (T_ref), using consistent units (e.g., °C).
If your measurement is in °Plato, use a suitable separate conversion before entering SG; no automatic Plato conversion is provided here.
Compute the density of pure water at T_meas and T_ref, then apply: SG_corr = SG_meas × ρ_w(T_ref)/ρ_w(T_meas).
If desired, convert SG_corr back to °Plato.
Choose Brewing hydrometer temperature in the Solve for selector, then Calculate.

Example Problem:

Use the following variables as an example problem to test your knowledge.

measured specific gravity = 1.05 SG

sample temperature (T_meas) = 25 °C

calibration temperature (T_ref) = 20 °C

Gravity Correction Calculator screenshot