Hydrometer Temperature Correction

Adjust specific gravity readings taken at non-calibration wort temperatures with ASBC thermal expansion polynomials.

Hydrometer Temperature Correction

Thermal expansion adjustment based on the ASBC polynomial equation

Measured Specific Gravity (SG)The raw uncorrected reading read from the hydrometer stem.

Measured Wort Temperature (°F)Temperature of the wort sample in the test hydrometer jar.

Hydrometer Factory Calibration Standard

Stamped on the paper scale inside your hydrometer glass bulb.

True Corrected Specific Gravity

1.058

+8.4 gravity points offset

Raw Hydrometer1.050

Temp Difference+50°F

As temperature rises, wort liquid expands and becomes less dense, causing the hydrometer to sink deeper and register a deceptively low reading. The corrected value represents the true density at calibration temperature.

Mathematical Formula & Derivation

ASBC Liquid Thermal Expansion Polynomial

SG_{\text{corrected}} = SG_{\text{measured}} \times \frac{c(T_{\text{measured}})}{c(T_{\text{calibrated}})}

Where c(T) = 1.00130346 - 0.00013472212·T + 0.0000020405259·T² - 0.00000000232820948·T³. Adjusts for liquid density expansion at elevated temperatures.

How to Use This Tool

1Take your hydrometer reading from the test jar and record the raw uncorrected SG (e.g. 1.050).
2Immediately measure the temperature of the wort sample using a digital thermometer (e.g. 110°F).
3Confirm your hydrometer calibration standard (printed on the internal scale, usually 60°F in the US or 68°F in Europe).
4The calculator displays true corrected specific gravity and the exact gravity point offset.

Tested Hardware Recommendation

Recommended Equipment for this Tool

Editorial Score: 93/100

NIST-Traceable Benchmark Specific Gravity Kit4.8 (2150 reviews)

Brewing America Triple Scale Hydrometer & Glass Test Jar Set

Cheap imported hydrometers are notoriously inaccurate, often off by 4-6 specific gravity points. Brewing America's hydrometers are hand-calibrated in the USA to NIST-traceable standards. Includes a crystal-clear heavy borosilicate glass test cylinder that won't cloud or scratch like cheap plastic cylinders, plus a microfiber cleaning cloth and storage case.

View on Amazon ($34.95)ASIN: B001X27L9W • Tag: homebrew079-20

Frequently Asked Questions

Why does warm wort give a false low reading on a hydrometer?

Liquids expand when heated, decreasing their density. A less dense warm wort offers less buoyant upward force, causing the glass hydrometer to sink deeper into the cylinder and show a falsely low gravity reading.

Can I measure boiling wort directly with a hydrometer?

Never place a standard glass hydrometer in boiling wort (212°F). Thermal shock will shatter the glass bulb, and hot wort can warp acrylic test cylinders. Always chill your test sample below 120°F before taking a reading.