Input
How to use this calculator
Enter current volume, current gravity, target gravity and your measured boil-off rate. The page determines whether the batch is too strong or too weak. For a weak batch, the boil-off rate helps estimate additional boiling time; for a strong batch, the result estimates water to add.
Use measured post-boil or pre-fermentation values from a well-mixed sample. Keep volume and gravity measurements tied to the same stage of the process.
How the calculation works
The implementation conserves gravity points multiplied by volume. If gravity is too high, it calculates the volume needed at the target points and reports water to add. If gravity is too low, it estimates fermentable additions using the configured DME, LME and sugar potentials and also reports a possible evaporation path.
The result assumes complete mixing and ignores changes caused by trub, evaporation composition and fermentation. Weigh additions and remeasure after the batch has equilibrated.
Example calculation
If 20 L is at 1.055 and the target is 1.050, the calculator identifies an over-strength batch and estimates dilution volume. If the current gravity is below target, it presents fermentable options rather than pretending water alone can increase gravity.
Understanding the result
Gravity adjustment is a rescue and planning tool. It helps decide whether dilution, additional extract, sugar or continued evaporation is the least disruptive correction.
Any correction changes the recipe balance. Water changes bitterness and color concentration, while sugar or extract changes fermentability, body and flavor. Record the correction as part of the brew history.
Common mistakes
- Mixing pre-boil and post-boil volumes.
- Correcting from a sample that was not fully mixed.
- Assuming sugar and malt extract have the same brewing effect.
- Adding a calculated amount without rechecking gravity.
Frequently asked questions
What should I do if gravity is too high?
The calculator estimates water needed to reach the target at the selected volume. Add gradually, mix thoroughly and remeasure.
Can boiling fix a weak wort?
Boiling concentrates gravity, but the time depends on your measured boil-off rate and can change bitterness and color.
Will adjustment preserve the original recipe?
No correction is neutral; document how water, extract or sugar changed the batch.
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