Coffee Ratio Calculator

Coffee Brewing Guide

What's the key thing to understand about The Golden Ratio?

The Specialty Coffee Association recommends a ratio of 1:15 to 1:18 (coffee to water by weight) for most filter brewing methods. 1:15 produces a stronger, bolder cup. 1:17 is the widely-used SCA standard for a balanced cup. 1:18 produces a lighter, more delicate cup. Espresso uses a much more concentrated ratio of 1:2 to 1:2.5 (e.g., 18g coffee yields 36–45ml espresso).

What's the key thing to understand about Ratios by Brew Method?

Filter / pour-over (V60, Chemex, Kalita): 1:15 to 1:17. French press: 1:12 to 1:15 (coarser grind, more forgiving). AeroPress: 1:10 to 1:16 (highly variable — one of the most flexible brewers). Moka pot: uses volume not weight — fill basket to top, water to valve level. Cold brew: 1:4 to 1:8 concentrate (dilute 1:1 to 1:3 before drinking). These are starting points — adjust to taste.

What's the key thing to understand about Grind Size and Extraction?

Grind size dramatically affects extraction. Too fine (over-extracted): bitter, harsh, astringent. Too coarse (under-extracted): sour, weak, tea-like. As a guide: extra fine for Turkish, fine for espresso, medium-fine for pour-over, medium for filter machines, medium-coarse for French press, coarse for cold brew. Water temperature matters too: 90–96°C for most methods (just off the boil). Boiling water extracts bitter compounds.

What should I know about Water Quality?

Coffee is 98% water — water quality matters enormously. Ideal mineral content for extraction: 75–250 mg/L total dissolved solids, with balanced magnesium and calcium. Soft water (low TDS) produces flat, lifeless coffee. Hard water (high TDS, high calcium) makes coffee dull and masks acidity. Filtered water or bottled still water is the easiest upgrade for most home brewers. Avoid distilled water — it extracts poorly and tastes empty.

What should I know about Coffee-to-Water Ratio Math?

Ratios like 1:15 or 1:17, which this calculator uses to produce the coffee_grams output, describe the proportion of coffee mass to water mass (or near-equivalent volume, since water is close to 1g per mL) — a 1:15 ratio means 1 gram of coffee for every 15 grams of water. The Specialty Coffee Association's commonly cited "golden ratio" range sits roughly between 1:15 and 1:18, with the stronger end of that range (closer to 1:15) producing a bolder cup and the weaker end (closer to 1:18) producing a lighter one, independent of how dark the roast is. Because the ratio is proportional, scaling a brew up or down for more or fewer cups just means keeping the same ratio while changing both numbers together — which is exactly what this calculator does when you change the water_ml input. If your usual result tastes consistently weak or over-extracted and bitter at the ratio you've been using, adjusting the ratio itself (rather than just grind size or brew time) is often the simplest first change to try.

What should I know about TDS and Extraction Yield?

Two more technical measurements sit behind what "brew strength" really means in specialty coffee: Total Dissolved Solids (TDS) and Extraction Yield. TDS measures the concentration of dissolved coffee compounds in the finished brewed coffee itself, usually expressed as a percentage, with a typical filter coffee target around 1.15–1.35% TDS — this is what most people mean when they describe a cup as "strong" or "weak." Extraction yield, by contrast, measures what percentage of the dry coffee grounds' total soluble mass actually ended up dissolved into the water, with an ideal target commonly cited around 18–22%. These two measures aren't the same thing: a brew can be strong (high TDS) by using more coffee at a normal extraction, or weak (low TDS) using less coffee even at a perfectly good extraction percentage. Under-extraction (below roughly 18%) tends to taste sour and underdeveloped because the easily dissolved pleasant compounds haven't fully come out yet, while over-extraction (above roughly 22%) tends to taste bitter and harsh as less desirable compounds from deeper inside the coffee particle start dissolving. Grind size, water temperature, and contact time are the main levers for shifting extraction yield, while the coffee-to-water ratio from this calculator is the main lever for shifting TDS strength.

What should I know about Adjusting Ratio for Milk-Based Drinks (Espresso)?

Espresso-based milk drinks use a fundamentally different ratio logic from filter or cafetière coffee, because the espresso itself is brewed at a much more concentrated ratio before milk is added. A standard single espresso shot uses roughly 1:2 coffee-to-water ratio by weight (for example, 18g of ground coffee producing around 36g of brewed espresso), which is far more concentrated than the 1:15-1:17 ratios typical of filter coffee, reflecting both the finer grind and the pressure-driven, shorter extraction time of espresso brewing. Once brewed, the espresso-to-milk ratio then determines the drink style: a flat white or cortado uses a small amount of milk relative to a strong coffee flavour (roughly equal parts espresso and steamed milk, with minimal microfoam), a latte uses considerably more milk relative to the espresso (often 1:3 to 1:5 espresso to milk) for a milder, milkier drink, and a cappuccino sits between the two with a thicker layer of foam on top. Getting the espresso extraction itself right (the 1:2 brew ratio, correct grind, and roughly 25-30 second extraction time) matters more to the final drink's quality than the milk ratio, since a poorly extracted (sour, under-extracted or bitter, over-extracted) espresso can't be rescued by any amount of milk.

Worked Example: Dosing Coffee for a 1-Litre French Press

A commonly cited French press ratio is around 1:15 (coffee to water by weight), on the stronger end of brewed-coffee ratios. For 1 litre (1,000g) of water, that gives 1,000 / 15 ≈ 67g of coffee. At the lighter end of typical filter-coffee ratios, around 1:17, the same litre of water needs 1,000 / 17 ≈ 59g. Since 1 level tablespoon of ground coffee is roughly 5-6g, 67g is in the region of 11-12 tablespoons, giving a quick practical way to measure a batch without scales once the target gram figure is known.

Water Temperature and Extraction

The Specialty Coffee Association and most brewing guides recommend brewing water around 90-96°C (just off a full boil) for most methods, since this range is hot enough to extract the full range of desirable flavour compounds without extracting so aggressively that bitter, overly tannic compounds dominate. Water that's too cool, well under about 85°C, under-extracts, often tasting sour, weak or flat because desirable flavour and aroma compounds haven't been pulled out of the grounds in sufficient concentration. Water straight off a hard boil (100°C) can over-extract fine grounds in particular, pulling out excess bitterness; letting freshly boiled water sit for 30-60 seconds (longer at higher altitude, where water boils at a lower temperature anyway) is a simple way to land in the ideal brewing range without needing a thermometer.

Why Grind Size Needs to Match Brew Time

Grind size and brew contact time work together to control extraction: a method with a short contact time, such as espresso (around 25-30 seconds), needs a very fine grind to extract enough flavour in that short window, while a method with a long contact time, such as cold brew (12+ hours), uses a coarse grind specifically because fine grounds left in contact with water for that long would over-extract into an unpleasantly bitter, harsh result. Using the wrong grind for a given brew time, fine grounds in a long-steep method, or coarse grounds in a fast method, is one of the most common reasons a correctly measured coffee-to-water ratio still produces a disappointing cup.

Why Pre-Ground Coffee Loses Strength Over Time

Ground coffee has far more surface area exposed to air than whole beans, which speeds up the loss of the volatile aromatic compounds responsible for fresh coffee's flavour and accelerates staling through oxidation, meaning pre-ground coffee that's been sitting for days or weeks needs a slightly more generous ratio to reach the same perceived strength as freshly ground coffee of the same type. Grinding beans immediately before brewing, rather than buying pre-ground coffee or grinding well in advance, is consistently recommended by coffee professionals as the single change most likely to improve a cup's flavour, often mattering more to the final result than fine adjustments to the coffee-to-water ratio itself.