Coffee tastes too bitter
The cup tastes sharply bitter or harsh rather than balanced.
Applies to: Espresso machine, V60 (pour-over), Moka pot, Espresso
Why coffee turns bitter
CoffeeHQ explanation
The more of a coffee you dissolve, the more of its bitter and drying compounds end up in the cup, and past a point they outweigh everything else. A brew that carries on too long, or works too efficiently, crosses that point. That is over-extraction, and it is the usual explanation for bitterness in coffee that was otherwise good. Strength plays at least as large a part. In the one trained-panel study of drip coffee CoffeeHQ has read, bitterness and astringency rose with the strength of the brew and showed no significant link to how far it had extracted, so a strong cup can taste bitter without being over-extracted at all.
The second source is the roast itself. Roasting creates bitter compounds, and the darker the roast the more of them there are. Bitterness of that kind is in the bean and no change of recipe will remove it; brewing more gently only softens it. If every brew of a particular coffee is bitter however you adjust it, the coffee is the answer.
Old coffee oil is the third and the most overlooked. Oils left in a grinder, a basket or a pot turn rancid, and rancid oil tastes sharply bitter. It taints fresh coffee brewed through the same equipment.
Causes, most likely first
There are 3 likely causes, listed with the most probable first. Work down the list and change one thing at a time, so that when the problem goes away you know which change fixed it.
Cause 1 of 3 · Commonly the cause
More was taken from the coffee than tastes good (often called over-extraction), or the brew is simply strong: the taste alone does not say which
- How to check
- Does the brew also taste hollow or harsh, not just bitter?
- What to change
- Add a little hot water to the cup first. If the bitterness fades, use a little less coffee. If it stays, use a slightly coarser grind, or reduce contact or brew time.
Cause 2 of 3 · Commonly the cause
Water too hot for the roast level
- How to check
- Are you using freshly boiled water straight off the boil?
- What to change
- Lower water temperature, especially for darker roasts.
Cause 3 of 3 · Reported, not independently verified
Stale or very dark-roasted beans
- How to check
- Is the bitterness present even after adjusting grind and temperature?
- What to change
- Use fresher beans or a lighter roast if bitterness persists after adjusting brew variables.
If none of these fixes it
Check the cleaning and descaling guide. Equipment that needs maintenance can cause several of these symptoms at once, and no change of recipe will correct it.
Work through it for your setup
The causes above are general. These go to the part of a diagnostic that takes this symptom one check and one change at a time.
- Make my coffee betterChoose your brewer and tick what you noticed
- Dialling in filter coffee: the same symptom, different causes
- Bitter, smoky or ashy however it is brewed, or a new dark coffee that brews unlike the last oneThe possibilities, the quickest check and one thing to change first
Add a splash of hot water before touching the grinder
A little hot water in the cup tells you which problem you have, and costs nothing. If the cup turns pleasant, it was too strong: use a little less coffee for the same water next time and leave the grind alone. If it stays harsh and drying when thinner, extract less: grind a step coarser and keep the recipe otherwise the same.
The order matters because the two fixes point the same way. Either makes the cup less intense, so trying both at once improves it whichever was needed and teaches you nothing for the next bag.
How it shows up on different brewers
Tendency, not a guarantee
- Espresso
- A shot that drips slowly and runs well past 35 seconds is over-extracting. Grind slightly coarser, or stop the shot a few grams sooner.
- Pour-over
- If the brew took much longer than usual to drain, the grind is too fine and the bed has choked. Grind coarser and pour a little more gently.
- French press
- Coffee left sitting on the grounds after pressing keeps extracting. Pour the whole brew out as soon as it is plunged.
- Moka pot
- Bitterness here is nearly always heat. Use a lower flame and take the pot off as soon as the stream turns pale and starts to sputter.
When it is the tap water and not the brewing
Water with a lot of bicarbonate neutralises a coffee's acids. In one controlled tasting of a single coffee, rising bicarbonate left the brew less acidic and fruity and more bitter and roasted, with nothing else changed. If every coffee you brew at home tastes flat and bitter and the same coffees taste livelier elsewhere, brew one cup with a bottled water of low stated bicarbonate before changing anything else.
Easily confused with
- Sourness — Sour is sharp and quick, makes the mouth water, and fades fast. Bitter builds more slowly and lingers after you swallow. They need opposite fixes, so it is worth pausing to decide which one you have.
- Coffee that is simply too strong — Very concentrated coffee can read as bitter even when it is well extracted. If adding a splash of hot water makes the cup pleasant, the problem was strength, and the fix is the ratio and not the grind.
What not to change at the same time
Do not grind coarser and use less coffee in the same brew. Both make the cup less intense, so it will improve whichever one was needed, and you will not know which to keep.
How to tell it is fixed
A well-extracted cup still has some bitterness: it is part of coffee. What should go is the harsh, drying edge that lingers after you swallow. Stop adjusting when the finish is clean, because going further tips the cup into sourness.
Understand the science: Coffee extraction — Strength and extraction are separate numbers; the panel result on bitterness is set out there.
Related issues
What to change
Specific adjustments for this symptom, with what each one trades off.
- AeroPress coffee tastes bitter, harsh or dry
- Pour-over coffee tastes bitter, dry or drains too slowly
- French press coffee tastes bitter or harsh
- Espresso tastes bitter, harsh or dry
- Bean-to-cup coffee tastes bitter or harsh
- Adjustable espresso machine shot tastes bitter
- Pod coffee tastes bitter, thin or watery on longer drinks
- Filter coffee machine coffee tastes bitter or stale
Work it out
Interactive tools that take you through this one change at a time.
Learn the technique
Step-by-step guides to the skills this problem comes from.
- Dialling in espressoFind the grind setting and recipe that make a particular coffee taste as intended, and be able to return to it.
- Adjusting grind sizeMove the grind in the right direction by a useful amount, and know what to expect from the change.
- Dialling in filter coffeeFind the grind and ratio that suit a particular coffee in a particular brewer, using brew time as a reading and never as a target.
- Tasting coffee deliberatelyNotice what a coffee is actually doing, rather than only whether you like it.
- Cupping coffeeTaste several coffees against each other under conditions identical enough that the only difference is the coffee.
- Measuring extraction yieldTurn a TDS reading into an extraction percentage, and know what that number can and cannot tell you.