Wort Dilution & Boil-Off Calculator

Calculate water additions to dilute over-gravity wort or boil durations to concentrate pre-boil gravity.

Wort Dilution & Boil-Off Evaporation

Enthalpy and mass balance equations for adjusting wort volume and gravity

Current Wort Volume (Gallons)

Current Measured Specific Gravity (SG)

Desired Target Specific Gravity (SG)Must be lower than current SG to calculate dilution water addition.

Dilution Water to Add

1.37 gal

5.5 quarts (5.20 liters)

Final Wort Volume6.87 gal

Target Density1.052 SG

Always use boiled or deoxygenated sterile water when diluting post-boil wort to prevent contaminating cold-side yeast fermentation.

Mathematical Formula & Derivation

Conservation of Gravity Points Mass Balance

V_1 \times GU_1 = V_2 \times GU_2

Gravity units (GU = (SG - 1) × 1000) represent total dissolved sugar mass. Because water additions contain 0 GU, total dissolved points remain constant while volume changes.

How to Use This Tool

1Select Dilution Mode if your mash efficiency was higher than expected and OG is too high.
2Enter current volume and current measured SG, then enter your desired target SG.
3The calculator outputs exact gallons, quarts, and liters of sterile water to add.
4Select Boil-Off Mode to calculate post-boil concentration based on kettle evaporation rate and boil duration.

Tested Hardware Recommendation

Recommended Equipment for this Tool

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Frequently Asked Questions

Should I dilute in the boil kettle or the fermenter?

Diluting in the boil kettle before or at flameout is safest because boiling sterilizes the water. If diluting in the fermenter, always boil and chill your dilution water first to prevent bacterial contamination and oxidation.

How do I determine my kettle's evaporation rate?

Boil a known volume of water (e.g. 6.0 gallons) for exactly 60 minutes with your normal burner flame and kettle lid off. Measure remaining volume. The difference in gallons is your system's hourly evaporation rate (typically 1.0 to 1.5 gal/hr).