The Two Knobs That Control Your Cup

If your coffee tastes wrong — too bitter, too sour, too weak, too strong — the answer almost always lives in two places: how coarse your grind is, and how much coffee you used relative to your water. Get these right and most other mistakes become minor.

What Grind Size Actually Does

Water extracts flavour from ground coffee over time. Finer grinds have more surface area, so extraction happens faster. Coarser grinds slow things down.

Too fine and you over-extract: the coffee tastes bitter, harsh, or astringent. Too coarse and you under-extract: sour, thin, or hollow.

A rough guide to grind sizes by method:

  • Coarse (sea salt texture) — French press, cold brew
  • Medium-coarse — Chemex, some clever drippers
  • Medium (sand texture) — flat-bottom drippers, Aeropress (longer steep)
  • Medium-fine — V60, Kalita Wave
  • Fine (table salt or finer) — Moka pot, some Aeropress recipes
  • Extra fine — espresso only

A burr grinder will give you a consistent, even grind. Blade grinders chop unevenly and make it very difficult to dial anything in reliably. You do not need an expensive grinder to start, but a basic burr model makes a real difference.

Coffee-to-Water Ratios

The standard starting point most specialty coffee guides agree on is 1:15 to 1:17 — that is, 1 gram of coffee for every 15 to 17 grams of water.

A 15g coffee to 250ml water ratio (roughly a standard mug) is a good first brew. Scales cost very little and remove the guesswork entirely. Volume measures (scoops, tablespoons) are inconsistent because different coffees have different densities.

Stronger or weaker? Adjust the ratio first before touching the grind. If you want a stronger cup, use 1:14 or 1:13. Weaker, try 1:18. Only adjust grind when you are chasing specific flavour notes — brightness, sweetness, body.

Tasting and Adjusting

Brew, taste, then ask yourself:

  • Bitter or harsh? Grind coarser, or reduce brew time.
  • Sour or thin? Grind finer, or extend contact time.
  • Flat, no flavour at all? Your beans might be stale — no ratio will fix that.

One change at a time is the only way to actually learn what made a difference. Change the grind and the ratio in the same brew and you will not know which one fixed it.

Water Matters More Than You Think

Hard or heavily chlorinated tap water will dull your coffee noticeably. Filtered tap water is fine for most people. You do not need specialist coffee water, but if your tap water tastes unpleasant on its own, use a Brita or similar filter.

Water temperature: aim for 90–96 °C. Just off the boil (let it sit for 30 seconds after boiling) is close enough without a thermometer.

Grind and ratio are the foundation. Once you understand what each one does, everything else in brewing becomes much easier to troubleshoot.