Wine Grapes Direct Juice & Must Adjustment Winemaking Calculator

© 2026 Wine Grapes Direct. All rights reserved. This calculator (including its design, text, and code) is proprietary to Wine Grapes Direct. Unauthorized copying, embedding, or redistribution is prohibited.
Disclaimer: Educational tool only. Results are estimates. You are responsible for measurements, bench trials, sensory evaluation, and final decisions. Do not scale up without confirming results on your specific must/juice.

Key assumptions & model notes

  • Projected liquid volume drives the math. For must, projected liquid is approximated as f × must volume (typ. 0.60–0.80). For juice pails, f = 1. If you enter an override, it wins.
  • Brix (°Bx) treated as sugar mass percent. Other solutes are ignored for this adjustment math.
  • Dilution conserves sugar mass. Water-back uses Vwater = (Bi/Bf − 1) × f × Vinitial (density differences ignored; accurate enough for typical use).
  • Acidulated water: When adding water, we assume it’s acidulated at your chosen g/L. The tool gives the exact grams for the water volume.
  • Chaptalization is a rule of thumb. Sugar additions use selected factor g/L per +1 °Bx. Dissolve fully; retest Brix.
  • pH response varies. We display three illustrative bands (Low/Medium/High response). Always bench trial when possible.
  • Tartaric cap: Default max is 35 g per 5 gal pail (scaled by pails) to reduce sensory risk. You can change the cap.
  • Water quality matters: Assumes chlorine-free, low-mineral water. Hard/chlorinated water can negatively affect wine.
  • Potassium heuristic (context only, not a prediction): Higher K can drive pH rise during fermentation via tartrate precipitation dynamics. High K often means outcomes tend toward more buffering / lower apparent response and less predictability.
  • How recommendations are chosen (important):
    • Conservative Start = the largest dose that stays above the target pH in the High Response worst case (and above style floor).
    • Balanced One-Shot = the largest dose that stays above the style floor in the High Response worst case (and within your max cap).
    • Bench plan (3 steps) = start with Conservative Start, then walk toward Balanced One-Shot with two follow-ups (retest each time).
Potassium charts used by this tool (for transparency)
Must (buffering tendency chart)
< 900 mg/L — Direct response (lower buffering tendency)
900–1100 — Mild buffering tendency
1100–1300 — Noticeable buffering tendency
1300–1500 — High buffering tendency
1500+ — Strong buffering tendency
Juice (risk bands chart)
< 800 mg/L — Low
800–1000 — Moderate
1000–1200 — Elevated
1200–1400 — High
1400+ — Very high

Inputs

Batch & units

Used to estimate total volume if you choose “number of pails.”
Math is done internally in liters; results display in your unit.
Pick one input mode. “Number of pails” auto-fills volume.
Copied into results when you click “Copy Results.”

Projected liquid (juice) volume

Must typically yields ~60–70% liquid. Choose higher only if you truly expect it.
If you know actual liquid volume, enter it here (wins).
House rule cap (scaled by pails). You can change it.

1) Brix adjustment

If Target < Current → dilution (water-back). If Target > Current → chaptalization (add sugar). Use chlorine-free, low-mineral water for any additions.
Rule of thumb for adjustment water. Tool outputs exact grams for your water volume.
Rule of thumb only. Bench test if precision matters.
If you dissolve sugar in water: use the smallest practical amount of chlorine-free, low-mineral water. Acidulate that water at the selected tartaric rate (shown in results).

2) pH target (tartaric additions)

This tool shows illustrative response bands and recommendations. Bench trials are strongly recommended.
Optional. Used only for a heuristic note (not a prediction).
Milestones are display points. More milestones = finer resolution.
Runs and updates the Results panel.

Results

Practical: dissolve tartaric fully, mix hard, wait 15–30 min, re-test pH. Sugar: dissolve fully, mix, re-check Brix.

Red Wine

The step-by-step guide linked below details how to make red wine with our pails of frozen red grape must.

Link to PDF


The file linked below covers how to make white wine with one of our pails of frozen white grape juice.

Link to PDF

White Wine


The file linked below covers how to make white wine with one of our pails of frozen white grape juice.

Link to Blog

Cider


 

More winemaking videos


Be sure to explore our Blog for ongoing tips on winemaking. And if you have any questions, shoot us an email at andrew@winegrapesdirect.com.