How the date is estimated
The calculator takes the °Brix change between your two samples and divides it by the days between them to get a daily rate (shown per week). The days left are the °Brix still to gain divided by that rate; the date is the latest sample’s date plus those days.
Potential alcohol at the target comes from the same must-weight conversion GrapeFlow uses (OIV sugar table), with 16.83 g/L of sugar per % vol for white, rosé and sparkling base and 17 g/L for red.
pH and titratable acidity are compared with typical ranges for the style. They often decide the date for whites and sparkling base, where you pick for freshness before sugar is high.
Example
A red block is at 20.5 °Brix on 1 September and 22.0 on 8 September: 1.5 °Bx a week. To reach 24.5 °Brix it needs 2.5 °Bx more, about 12 days — around 20 September — with a potential alcohol of about 14.5 % vol.
Frequently asked questions
How often should I sample?
Weekly from veraison, then every two or three days as you near the target. More frequent samples make the trend — and the date — more reliable.
Why did °Brix drop after rain?
The vines take up water and the berries swell, diluting the sugar. It usually recovers within a few dry days; wait before reading a trend into it.
What target °Brix should I use?
The one that fits your wine: lower for sparkling base and fresh whites, higher for full reds. The defaults are common starting points, not rules.