Gravity Dilution Calculator
Overshot your gravity? Work out exactly how much water brings it back to target — or what blending two batches will give you.
Volumes can be any unit as long as both sides use the same one — the maths is a ratio.
How this was worked out
water = (60.0 points × 5) ÷ 50.0 points − 5 = 1.000
The sugar in the vessel does not change when you add water — only the volume it is spread through. So gravity points times volume stays constant.
Why the maths runs on gravity points
Adding water changes nothing about the sugar in your kettle. The same dissolved extract is simply spread through more liquid. That means the total quantity of sugar — gravity points multiplied by volume — stays constant, and everything else follows from rearranging that one relationship.
It has to be points rather than raw specific gravity, because the 1 in a reading like 1.048 is just water and does not dilute. Only the 48 points represent anything dissolved. Average the full readings instead of the points and the answer drifts wrong in a way that is easy to miss and hard to spot later.
Worked example
You have 5 gallons at 1.068 and wanted 1.055.
water = (68 × 5) ÷ 55 − 5 = 1.18 gallons
Adding that brings you to 6.18 gallons at 1.055 — the target, confirmed by running the dilution the other way.
Blending is the same idea weighted by volume: 3 gallons at 1.060 combined with 2 at 1.040 gives 1.052.
What each gallon of water does
Starting from 5 gallons at 1.068, each addition moves gravity less than the one before — the same sugar spread through a progressively larger volume.
| Water added | Total volume | Resulting gravity | Points |
|---|---|---|---|
| 0.00 gal | 5.00 gal | 1.0680 | 68.0 |
| 0.25 gal | 5.25 gal | 1.0648 | 64.8 |
| 0.50 gal | 5.50 gal | 1.0618 | 61.8 |
| 0.75 gal | 5.75 gal | 1.0591 | 59.1 |
| 1.00 gal | 6.00 gal | 1.0567 | 56.7 |
| 1.50 gal | 6.50 gal | 1.0523 | 52.3 |
| 2.00 gal | 7.00 gal | 1.0486 | 48.6 |
Common mistake
Diluting to hit a gravity target without checking whether the fermenter can hold the result. Correcting a high-gravity batch frequently pushes the volume past what your vessel has headspace for, and the fix — leaving some behind — changes the numbers again. Work out the final volume before adding anything.
Keep going
- Diluting wort lowers gravity and therefore final strength; the ABV calculator shows what the new numbers work out to. ABV Calculator
- Dilution maths runs on specific gravity, so a refractometer reading needs converting first. Brix ↔ gravity Calculator
Frequently Asked Questions
Does it matter whether I work in gallons or litres?
No. Dilution is a ratio, so as long as both volumes use the same unit the answer is the same. Five gallons diluted by one gallon behaves identically to five litres diluted by one litre.
Can I use this to raise my gravity?
Not by dilution — adding water can only lower it. To raise gravity you either boil longer to drive off water, which concentrates what is left, or add malt extract. The calculator returns a negative water figure if you ask for a higher target, which is its way of saying the request is impossible.
Why does the maths use gravity points rather than specific gravity?
Because points scale linearly and specific gravity does not. The 1 in 1.048 is just water; only the 48 points represent dissolved sugar. Diluting halves the points, not the whole reading — averaging specific gravities directly would give a subtly wrong answer every time.
Should I account for the wort I lose to trub and hops?
Yes, in the sense that your starting volume should be the volume you actually have, not what the recipe assumed. Losses to hop absorption and trub are often a litre or more, and using the theoretical figure will leave your corrected gravity off by the same proportion.
Is blending two finished beers the same calculation?
For gravity, yes — it is the same weighted average by volume. Everything else about blending, from bitterness to colour to whether the result tastes like anything, does not follow gravity and needs judging separately.
A note on method. Every figure on this page comes from conservation of dissolved extract — gravity points times volume is constant — rather than from a fitted formula, so there is no external constant to cite. This is a calculation tool for homebrewing and says nothing about consumption.
Related Calculators
- ABV Calculator — Gravity & Alcohol
- Brix ↔ gravity Calculator — Gravity & Alcohol
- Attenuation Calculator — Gravity & Alcohol
- IBU Calculator — Hops & Bitterness