Cold brew is steeped, not brewed, and the whole craft lives in one ratio: how much coffee meets how much water. Get it right and the jar in your fridge pours sweet, smooth and strong; get it wrong and you have bottled regret for a week. This cold brew ratio calculator works in both directions — coffee in hand or water in hand — across the standard strengths, from drink-it-straight to cut-it-half concentrate.
The Ratios, Translated
Cold brew ratios are written coffee-first by weight: 1:8 means one gram of coffee per eight grams (millilitres) of water — this page's default, turning 100 g of coffee and 800 ml of water into the standard fridge concentrate. The working range: 1:4 to 1:5 for heavy concentrate meant for heavy dilution or coffee cocktails; 1:8 the classic all-purpose concentrate; 1:12 a light concentrate or an assertive ready cup; 1:15 to 1:17 ready-to-drink strength with nothing to add. Working by weight matters because scoops lie — a tablespoon of beans varies by roast and grind far more than a scale ever does. If you must use volume, the rough bridge is 1 cup of whole beans ≈ 80–90 g, ground coarse.
Serving Math: Diluting the Concentrate
Concentrate exists to be cut. The house rule for 1:8 is one part concentrate to one part water or milk over ice, which lands the glass near 1:16 in-cup strength. Prefer it stronger or weaker and the calculator's ratio list is your ladder: dilute 1:8 at two-to-one for a gentle glass, or pour 1:4 concentrate nearly neat for a very serious one. Yield planning runs through absorption: grounds hold onto about twice their weight in water, so a 100 g / 800 ml batch returns roughly 600 ml of strained brew — five or six diluted glasses. Scale the batch to the week's drinking, because fresh cold brew peaks within about a week refrigerated even though it keeps safely for two.
Time, Grind and Temperature
Ratio is only one dial of three. Grind coarse — French-press territory; fine grounds over-extract into bitterness and silt through filters. Time: 12 to 24 hours covers nearly everything, room temperature steeping faster than the fridge; past 24 hours the cup trends woody. Temperature is the forgiving dial — cold and room-temperature water both work because time substitutes for heat, which is also why cold brew tastes sweeter and less acidic: the harsh acids and bitter compounds that hot water pulls quickly barely extract in a cold, slow steep. Blooming the grounds with a small pour of hot water first (a hybrid some cafés swear by) brightens the cup slightly; it is an accent, not a requirement.
Scaling From One Glass to a Batch
The calculator's two modes serve the two real questions. Coffee-first ("I have 100 g of beans") is batch planning from the bag. Water-first ("the jar holds a litre") is vessel planning: a litre at 1:12 needs 1000 ÷ 12 ≈ 83 g of coffee. Café-scale arithmetic is the same with zeroes added — a 10-litre 1:8 batch is 1.25 kg of coffee — though at that size, stir the slurry at the start and again midway, because a metre of grounds does not wet itself evenly by patience alone.
Cold Brew vs Iced Coffee
Not the same drink, and the ratio explains why. Iced coffee is hot coffee brewed at drip ratios (about 1:15 to 1:17) and chilled — bright, acidic, and diluting as its ice melts. Cold brew starts life at immersion ratios from 1:4 to 1:15 in unheated water — smoother, sweeter, naturally stronger per sip, and stable for days. Neither is "better"; they are different extractions wearing similar clothes. If a recipe says cold brew concentrate, swapping in yesterday's iced coffee will underwhelm it in a way no amount of chilling fixes.
Common Mistakes
Weighing in scoops and blaming the ratio. Grinding fine and steeping long — the two errors compound into a bitter, muddy jar. Under-steeping a fridge batch on a room-temperature schedule (cold slows extraction; give fridge batches the long end of the window). Forgetting absorption when planning yield, then coming up a glass short for guests. And storing the concentrate with the grounds still in it past a day: strain on schedule, because the steep does not stop just because you stopped watching it.
Related Tools
The coffee corner of the Food Calculators hub starts with the Coffee Ratio Calculator for hot brewing, while the ML to Grams Calculator converts any liquid measure on this page.
Frequently Asked Questions
What is the best cold brew ratio?
1:8 by weight is the classic concentrate — 100 g coffee to 800 ml water — diluted about 1:1 to drink. Use 1:4 for heavy concentrate, 1:12 for a light one, or 1:15 for ready-to-drink with no dilution.
How much coffee for 1 litre of cold brew?
It depends on strength: 125 g at 1:8, about 83 g at 1:12, or about 67 g at 1:15. Enter the litre in water mode and pick your ratio for the exact figure.
How long should cold brew steep?
12 to 24 hours — the shorter end at room temperature, the longer in the fridge. Coarse grounds, then strain; leaving grounds in past a day keeps extracting into bitterness.
Why is my cold brew weak or bitter?
Weak usually means too high a ratio (too much water per gram), too short a steep, or grounds measured by scoop instead of weight. Bitter usually means too fine a grind or a steep past 24 hours.
How much finished cold brew will I get?
Less than the water you poured: grounds absorb about twice their weight in water. A 100 g coffee / 800 ml water batch yields roughly 600 ml of strained concentrate.
How long does cold brew keep?
About a week at peak flavour in the fridge, up to two weeks safely if strained and sealed. Diluted servings are best within a couple of days.
Is cold brew stronger in caffeine than hot coffee?
Per undiluted sip of concentrate, yes — it is brewed at twice the concentration. Once you dilute it to drinking strength, a glass lands in the same neighbourhood as a strong hot coffee.