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Cold Brew Ratio Calculator

Cold brew requires precise measurement to achieve the smooth, less acidic concentrate you're after. Unlike hot drip coffee's 1:17 ratio, cold brew uses a stronger 1:5 coffee-to-water proportion due to its room-temperature steeping process. This calculator eliminates guesswork by determining how much ground coffee and water you need based on your desired batch size and preferred strength.

Last updated:

Creators Hanna Pamuła, PhD Food Science
7,948 people find this calculator helpful

Understanding Cold Brew Fundamentals

Cold brew differs from hot coffee in preparation method and chemistry. Rather than using hot water to quickly extract flavours and caffeine, cold brew relies on prolonged contact—typically 12 to 24 hours, with 16 hours being optimal—between coarse grounds and room-temperature water. This slow extraction produces a concentrate that's naturally lower in acidity and gentler on the stomach.

The most significant practical difference: concentration. A standard cold brew concentrate will reduce to about 80% of your initial water volume due to absorption and settling. This 20% loss means if you want 1 litre of finished concentrate, you'll need to start with 1.25 litres of water.

Strength preference varies widely. While the industry standard remains 1:5 (one part coffee to five parts water by mass), you can adjust to 1:4 for stronger concentrate or 1:6 for a milder version. Grind size matters too—aim for a coarse consistency, similar to French press grounds, to prevent over-extraction and ensure clean separation from the liquid.

Cold Brew Calculation Formula

These equations show how to convert your desired batch size into the precise amounts of coffee grounds and water needed:

Water Required (ml) = Concentrate Volume (ml) ÷ 0.8

Coffee Grounds (g) = Water Required (ml) ÷ Ratio Value

Caffeine Content (mg/ml) = (Coffee Grounds (g) × 13.94) ÷ Water Required (ml)

Coffee Grounds Volume (ml) = Coffee Grounds (g) × 2.15

  • Concentrate Volume — The final amount of cold brew concentrate you want to produce
  • Water Required — The starting volume of room-temperature water needed (accounts for the 20% reduction)
  • Ratio Value — The divisor in your strength ratio (5 for standard 1:5, 4 for 1:4 stronger brew)
  • Coffee Grounds — Mass of dry coffee in grams
  • Caffeine Content — Approximate caffeine concentration per millilitre of final brew

Caffeine Content and Strength Variations

A litre of standard 1:5 cold brew concentrate contains approximately 2,787 mg of caffeine—significantly more than the same volume of hot drip coffee. This elevated caffeine isn't accidental; it's a direct consequence of using more grounds per unit of water.

However, caffeine content scales linearly with your chosen ratio. Brewing at 1:4 increases caffeine by roughly 25%, while 1:6 reduces it by about 17%. The type of bean and roast level also affect caffeine: lighter roasts retain slightly more caffeine than dark roasts, though the difference is modest compared to the impact of your coffee-to-water ratio.

When calculating for custom batch sizes, remember that the final concentrate volume will be about 80% of your starting water volume. For example, if you want 500 ml of finished concentrate, begin with 625 ml of water. At a 1:5 ratio, you'd use 125 grams of grounds.

Acidity and Taste Profile

Cold brew's gentler acidity is one of its most valued characteristics. Research has measured cold brew at a pH of approximately 5.13, compared to 4.85 for hot drip coffee—meaning hot coffee is roughly twice as acidic. This difference isn't trivial for those with sensitive stomachs or acid reflux concerns.

The extended steeping at room temperature extracts fewer acidic compounds while allowing smooth flavours to develop fully. This is why many describe cold brew as cleaner and less bitter. The trade-off: you sacrifice some of the bright, vibrant notes that hot brewing can highlight.

Dilution strategy matters when serving. Most cold brew concentrates are diluted at a 1:1 ratio with water or milk before drinking, though some prefer stronger or lighter servings. Experiment within your preferred strength range to find your optimal concentration.

Common Cold Brew Pitfalls to Avoid

Precision and timing are essential for consistent results.

  1. Weighing Beats Guessing — Always measure coffee grounds by weight in grams rather than volume. Grind size, humidity, and bean density affect how tightly grounds pack, making volume measurements unreliable. A kitchen scale is inexpensive insurance against weak or oversteeped batches.
  2. Steeping Duration Matters — While 12 to 24 hours are acceptable, aiming for exactly 16 hours gives optimal flavour balance. Under 12 hours produces weak, under-extracted concentrate. Beyond 24 hours risks over-extraction and unpleasant astringency, especially with finer grinds.
  3. Temperature Control — Room temperature ideally means 18–22°C. If your kitchen is warmer, use cooler water or store the jar in a cooler spot to prevent rapid fermentation of oils. Conversely, unusually cold environments slow extraction; consider a slightly longer steep time.
  4. Filtration Technique — Use a fine mesh strainer or cheesecloth to separate grounds. If you skip this or use a coarse filter, sediment will muddy your concentrate. A two-stage filtration—first through metal mesh, then through a paper filter—yields the clearest result.

Frequently Asked Questions

Why does cold brew require a different ratio than hot coffee?

Hot water extracts coffee compounds rapidly—a 1:17 ratio achieves full extraction in minutes. Cold water requires far longer contact time and higher ground-to-water mass to extract sufficient flavour and caffeine over 12–24 hours. The 1:5 cold brew ratio compensates for the slow extraction rate. If you used hot coffee's weaker ratio, your cold brew would be unacceptably thin and caffeine-poor after steeping overnight.

How do I adjust my recipe for a weaker or stronger cold brew?

Strength adjusts by changing the ratio's divisor. For standard strength, use 1:5 (divide water volume by 5 to get grams of coffee). For stronger, try 1:4, which increases caffeine by roughly 25%. For milder, try 1:6, reducing caffeine by about 17%. Your final concentrate can also be diluted further when serving—many people add equal parts water or milk before drinking, so the concentrate's inherent strength is just the starting point.

Does the type of coffee bean affect cold brew results?

Yes, significantly. Single-origin beans and light roasts showcase distinct, nuanced flavours in cold brew's gentle extraction. Dark roasts tend toward chocolate and smoky notes. Lighter roasts retain slightly more caffeine, though the effect is modest compared to your coffee-to-water ratio. Fresh beans (roasted within 2–4 weeks) perform better than stale ones, as flavour oils degrade over time. Experiment with different origins to find your preference.

Can I use regular or fine-ground coffee for cold brew?

Coarse grounds are recommended because they steep fully while remaining easy to filter. Fine grounds work but risk over-extraction and are messier to separate from liquid. If you only have fine grounds, reduce steeping time by 2–4 hours and stir gently midway through. Never use coffee dust or grounds meant for espresso machines—they'll clog your filter and create muddy, bitter concentrate.

How long does homemade cold brew concentrate keep?

Properly strained and stored in an airtight container, cold brew concentrate lasts 7–14 days in the fridge. After two weeks, oils oxidise and flavour degrades noticeably. For longer storage, freeze in ice cube trays and thaw as needed; frozen concentrate keeps 2–3 months. Always use clean, dry containers to prevent mold growth, and ensure grounds are fully removed before refrigerating.

Is cold brew safe for people with acid reflux?

Yes, for many people. Cold brew's pH of 5.13 is roughly half as acidic as hot drip coffee at pH 4.85, making it gentler on the stomach and esophagus. However, individual tolerance varies—caffeine itself can trigger reflux in sensitive individuals regardless of acidity. If you're prone to reflux, start with small amounts of diluted cold brew and observe your symptoms. The lower acidity doesn't eliminate caffeine's effects, so those avoiding caffeine altogether should still moderate intake.

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