Home brewing fundamentals: Grind size, ratios & time

Written By 15grams

Balancing the three key variables to get the best out of your beans.

Ever wonder why your home-brewed coffee doesn't quite taste right? It's probably not your beans (assuming you're buying excellent quality specialty ones like ours ;) ). It's likely down to three key variables: grind size, water ratio, and brew time. Think of them as the volume, bass, and tempo knobs on your coffee's flavour profile. Let's break them down:

1. Grind Size: The Foundation of Flavour

Imagine you’re pouring water through one funnel with pebbles and another with sand, you can expect the water to pass through the pebbles a lot faster and therefore have less time to sit with the water whilst the sand takes longer for water to pass through. Similar to if you’re making pasta sauce; If you chop your onions super fine, they'll practically melt into the sauce, releasing all their flavour quickly. If you leave them in huge chunks, they'll take longer to cook and you'll get a more subtle onion flavour.

Coffee grind size works the same way:

  • Too Fine (like icing sugar): The water struggles to pass through, over-extracting the coffee. This leads to a bitter, harsh, and sometimes muddy taste. Think of it like over-steeping a tea bag – too much of the "bad stuff" gets pulled out.

  • Too Coarse (like chunky sea salt): The water flows through too quickly, under-extracting the coffee. This results in a weak, sour, and watery taste. It's like trying to make tea with barely any leaves – not enough flavour gets into the water.

  • Just Right (depends on your brew method): This is where trial and error should take you! The water extracts the perfect balance of flavours, giving you a sweet, balanced, and delicious cup.

Top Tip: A burr grinder (even a hand-cranked one) is much better than a blade grinder. Blade grinders chop unevenly, leading to inconsistent extraction. Burr grinders crush the beans uniformly. We recommend the Wilfa Grinder as a great quality grinder.

Grind Size Cheat Sheet (General Guidelines):

Extra Coarse: Cold Brew. Resembles coarsely cracked peppercorns or large, flaky sea salt.

Coarse: French Press/Cafetière. Similar to coarse sea salt or kosher salt.

Medium-Coarse: Chemex. Coarse sand or a rougher breadcrumb texture

Medium: Drip Coffee Makers, Pour-Over (like V60). Similar to sand.

Medium-Fine: Pour-Over (for some recipes), Aeropress. Somewhere between table salt and coarser granulated sugar

Fine: Moka Pot, Aeropress (short brew times). Slightly like caster sugar

Extra Fine: Espresso. Like icing sugar or flour.

2. Water Ratio: The Strength Slider

This one's pretty straightforward: it's the amount of coffee you use compared to the amount of water. The industry standard for brewing filter coffee is often expressed as a ratio, like 1:15. Stronger and weaker in this context is how much coffee flavour you want in your drink, and if you prefer a more diluted taste:

Stronger Coffee: Use a lower ratio (e.g. 1:12). More coffee, less water.

Weaker Coffee: Use a higher ratio (e.g. 1:18). Less coffee, more water.

A good starting point for most methods is 60g of coffee per 1 liter of water (which is a 1:16.67 ratio) or if 1 litre sounds like a ridiculous amount to drink at once, 15g of coffee per 250ml. But don't be afraid to experiment!

For espresso, 1:2 is the recommended ratio. So if you have 20g of beans in the portafilter, you can expect a 40g yield of espresso to come out of the machine.

Top Tip: Use a scale! It's the easiest way to be precise with your coffee and water measurements. Grams are your friend here, as 1ml of water weighs 1g. We recommend any digital scale that can measure to the gram.

Water Ratio: Cheat sheet (Guidelines)

Filter coffee/most home brewing methods: We recommend 15g coffee for 250ml water or 60g coffee per 1litre (1:16.67)

Cold Brew: 1:12 (recommended 80g to 1l water)

Home Espresso Machine: 1:2 coffee to extracted coffee. (e.g. if it’s 20g coffee in the portafilter then work to 40g extracted into your cup).

3. Brew Time: The Extraction Timer

Brew time is how long the water is in contact with the coffee grounds. It's directly related to grind size:

Finer Grind = Shorter Brew Time: There’s a higher rate of extraction, think small potato pieces boiling in a pan vs. large.

Coarser Grind = Longer Brew Time: The water needs more time to penetrate the larger particles e.g. throwing a big potato to boil in a pan.

General Brew Time Guidelines:

  • Cold Brew: 12-24 hours

  • French Press: 4 minutes

  • Pour-Over: 2.5-3.5 minutes

  • Moka Pot: Until it gurgles (then remove from heat and cool down with water immediately!)

  • Espresso Machine: aim for around 30s extraction time (remembering the 1:2 ratio of coffee to how much is extracting out into the cup)

  • Filter Coffee Machine: Varies, but usually 4-6 minutes e.g. Moccamaster, Aromaboy. These tend to do all the hard work

Taste Tweaks: Putting It All Together

Bitter/Stronger Coffee? Your grind is likely too fine, your brew time is too long, or your water ratio is too low (too much coffee). Try a coarser grind, shorter brew time, or a higher water ratio.

Sour/Acidic/Weak Coffee? Your grind is likely too coarse, your brew time is too short, or your water ratio is too high (too little coffee). Try a finer grind, longer brew time, or a lower water ratio.

Experiment and record. Make small changes to each brew, record what you did and then compare to previous brews.

If it’s still not working: a sneaky variable that you may find can be affecting your meticulous measuring is the age of the beans, as they slowly dry out the balance may need to be changed e.g. finer grind setting on your espresso machine if the coffee has been sitting out exposed in the hopper!

The Bottom Line: Don't be afraid to experiment! These are guidelines, not strict rules. Find the combination of grind size, water ratio, and brew time that you enjoy the most.

You can find all our brew guides on this page - Happy brewing!

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