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Chemex Coffee Calculator: Ratio, Recipe and Brew Guide

Dose, water, bloom, and ratio for any Chemex size. 1:16.7 starting point.

Size sets the capacity warning only, not the brew formula.

times dose

Range 2 to 3. Default 2 (2 g water per g coffee).

Brew Schedule

  1. Bloom

    Pour 3x dose weight in water (e.g., 126g for 42g dose) in a steady spiral; saturate all grounds and wait for the bloom to stabilize.

  2. First Pour

    Pour steadily to reach 40% of total water weight; spiral from center outward, do not hit the filter walls.

  3. Second Pour

    Once the level drops near the grounds, pour to 70% of total water; maintain a slow, even spiral.

  4. Final Pour

    Add remaining water to target weight; avoid disturbing the bed. Chemex draws slower than most pour-overs; this is expected.

  5. Drawdown

    Wait for the bed to drain completely; total time of 4:30-5:00 is expected. If it drips past 5:30, grind coarser next time.

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How to Use This Calculator

  1. Select Your Chemex Size

    Pick your brewer from the size dropdown. The size sets the capacity limit for the warning; it does not change the brew formula. The default is 6-cup.

  2. Enter Dose or Water

    Type your coffee dose in grams (or ounces) and the calculator derives brew water at the current ratio. Change the water field unit to mL, fl oz, or cups if you measure by volume.

  3. Adjust the Ratio

    The ratio field is live: change it and the water updates. The default 1:16.7 matches Chemex's own instructions and sits within the SCA filter range. Adjust by 0.5 points at a time, not by dose increments.

  4. Set the Bloom Multiplier

    The default is 2 times the dose (84 g for a 42 g dose). Adjust between 2 and 3 based on your preference. The result card shows bloom water and remaining pour water separately.

Chemex: Ratio, Filter, and Drawdown

The Chemex is a pour-over brewer designed around its thick bonded paper filter. Chemex papers are roughly 20 to 30% thicker than standard cone papers, filtering out the oils that a French press or metal filter would leave in. The result is a clean, light-bodied cup with exceptional clarity and low sediment. The trade-off is control: the slow drawdown means an under-ground bed stalls and over-extracts fast. Watch total brew time and adjust grind to stay in range.

The default ratio here (1:16.7, 42 g / 700 g) is what Chemex’s official instructions approximate and what most 6-cup Chemex recipes converge on. It sits within the SCA’s filter brewing target range. Start here and adjust by 0.5 ratio points at a time rather than by dose increments; the Chemex is sensitive enough that a 3 g dose change alters the drawdown time noticeably.

Grind medium-coarse: coarser than a V60, not quite as coarse as a French press. The reference is coarse sea salt. The Chemex filter is thicker and will compensate for a slightly finer grind compared to a standard cone dripper, but if you’re copying a V60 recipe directly, open up the grinder by a couple of clicks before you start. Not sure where your grind lands? Use the grind size guide to dial in.

Pour in pulses. Bloom with 2 times the dose weight (84 g for a 42 g dose), stir gently, wait 45 to 60 seconds. Then pour in two or three more additions, going circular, keeping the water level consistent. The goal is even saturation throughout the bed; aggressive pours that dig channels into the grounds produce uneven extraction. The total draw-down for a 700 g brew should be 4:30 to 5:30. If it runs faster, grind finer. If it stalls past 6:00, go coarser.

Parameters at a Glance

ParameterRecommendationNotes
Ratio1:16.7 (default)SCA filter range 1:15 to 1:18. Adjust by 0.5 points at a time.
Grind sizeMedium-coarseLike coarse sea salt. Coarser than V60, not quite French press.
Water temperature93 to 96 °C (200 to 205 °F)Just off the boil. Cooler end suits darker roasts.
Bloom2x dose, 45 to 60 seconds84 g bloom for 42 g dose. Stir gently; wait for bed to settle.
Brew time (6-cup)4:30 to 5:30Faster than 4:30, go coarser. Past 6:00, go finer.
Pour style3 to 5 pulse poursCircular pours, consistent water level. Avoid channeling.

Frequently Asked Questions

What is the best ratio for Chemex coffee?

Start at 1:16.7 (42 g coffee to 700 g water). That's the default here and matches what Chemex's own instructions approximate for a 6-cup brew. The SCA filter target range sits between 1:15 and 1:18. Adjust by 0.5 ratio points at a time rather than dose increments; the Chemex is sensitive enough that a small grind or ratio change alters drawdown noticeably.

How much water should I use for the Chemex bloom?

The default here uses 2 times the coffee dose. For a 42 g dose that means 84 g of bloom water. The valid range is 2 to 3 times the dose. Use the bloom multiplier input to adjust. Pour the bloom water slowly, stir gently, and wait 45 to 60 seconds before the main pour. The bloom releases CO2 and helps even saturation across the filter bed.

What grind size should I use for Chemex?

Medium-coarse, like coarse sea salt. Coarser than a V60, not quite as coarse as a French press. The Chemex's thick bonded paper filter is 20 to 30% thicker than standard cone papers and compensates for a slightly finer grind compared to a standard cone dripper. If you're converting from a V60 recipe, open up the grinder by a couple of clicks before your first Chemex brew.

Why does the Chemex take longer to brew than a V60?

The thick Chemex paper filter restricts flow more than a standard cone paper. That slower drawdown is intentional: it filters out more oils, producing a cleaner, lighter-bodied cup. The trade-off is that an under-ground bed can stall and over-extract. Total drawdown for a 700 g brew should land between 4:30 and 5:30. Faster than that, go finer. Slower than 6:00, go coarser.

How do I know which Chemex size to select?

Select the model you own. The size only affects the capacity warning, not the brew formula. Approximate capacities: 3-cup is 450 mL, 6-cup is 900 mL, 8-cup is 1100 mL, and 10-cup is 1500 mL. The calculator will flag you if your water amount exceeds the selected brewer's capacity so you can adjust before you start.

Timberline Coffee School

Trent built this calculator. He also runs Timberline Coffee School, where baristas and roasters train through SCA-accredited programs covering espresso, brew method, and sensory skills.

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