Sour coffee usually means under-extraction. The most common causes are a grind that’s too coarse, brew time that’s too short, water that’s too cool, or uneven extraction. Fix those first and sweetness will return.
Sour coffee tastes sharp, thin and slightly unfinished. Instead of balance and sweetness, acidity dominates and the cup feels hollow.
That’s different from bright acidity. Some coffees naturally taste lively, especially lighter roasts. Good acidity feels clean and structured. Sourness feels incomplete and unbalanced.
In most cases, the problem is simple. The water hasn’t pulled enough sweetness and body from the grounds, so the acids show up on their own. Below, you’ll see exactly what to adjust so your coffee tastes fuller and more balanced.
How to Fix Sour Coffee
If your coffee tastes sour, adjust one variable at a time. Sourness usually means the brew hasn’t developed enough sweetness. Start with the changes below and keep everything else consistent so you can see what improves the flavour.
- Grind finer. A coarse grind allows water to pass through too quickly, leaving the brew sharp and thin. Go slightly finer and taste again.
- Brew a little longer. If your espresso shot runs very fast or your pour over finishes too quickly, extend the contact time slightly.
- Increase water temperature. Aim for around 94-96°C. Water that’s too cool slows extraction and leaves acidity dominant.
- Increase the dose slightly. A touch more coffee can improve strength and balance if the cup feels weak and sour.
- Improve agitation. In pour over or cafetière brewing, gentle stirring or better pouring can help extract more evenly.
Why Coffee Turns Sour
Coffee extracts in stages. The brighter acids dissolve first, while sweetness and body develop later. If the brew runs too fast, too cool, or too coarse, extraction stops before balance is reached.
This is under-extraction. The cup tastes sharp and thin because the sugars and heavier compounds haven’t had time to dissolve. Slow the brew slightly and sweetness returns.
If the coffee feels dry and heavy instead of sharp, you may be over-extracting instead. Here’s how to fix bitter coffee properly.
A Quick Way to Pinpoint the Problem
Use this to quickly narrow it down. The way the coffee feels and finishes will usually tell you what needs adjusting. Focus on the texture and balance, not just the first sip.
Diagnose the sourness in seconds
Match the flavour to the likely cause, then change one variable at a time.
| If it tastes like | Likely cause | What to change |
|---|---|---|
| Sharp & thin | Under-extracted | Grind finer |
| Watery & acidic | Brew too short | Extend brew time |
| Sour espresso | Shot running too fast | Adjust grind |
| Flat & tart | Water too cool | Increase temperature |
The Most Common Causes of Sour Coffee
1) Grind is too coarse
If your grind is too coarse, water flows through too quickly. The shot or brew finishes before enough sweetness develops, leaving acidity exposed and the cup tasting thin.
Simple fix: Go slightly finer and keep everything else the same. If you’re unsure what grind size suits your brew method, see our guide on how to grind coffee beans properly.
2) Brew time is too short
Coffee needs enough contact time for balanced extraction. If you plunge early, stop your espresso shot too soon, or your pour over runs fast, you’ll mostly extract the brighter acids and miss the sugars that bring balance. The result is sharp and underdeveloped.
Simple fix: Extend the brew slightly. For cafetière, stay closer to four minutes. For espresso, aim for around 25-30 seconds. Make small adjustments so you can taste the difference clearly.
3) Water is too cool
Cooler water extracts more slowly and less effectively. If your brewing temperature is too low, it struggles to pull out the fuller, sweeter compounds. That leaves the cup tasting bright but hollow.
Simple fix: Increase your water temperature slightly. Aim for around 94-96°C. If you’re brewing with a cafetière, our guide to the ideal water temperature explains this in more detail.
4) Uneven extraction
If water doesn’t move evenly through the coffee bed, some areas extract properly while others barely extract at all. This is common in espresso when the puck isn’t prepared evenly, or in pour-over when the grounds aren’t fully saturated. The result can taste both sour and weak.
Simple fix: Improve distribution and agitation. In espresso, level and tamp evenly. In pour-over, make sure all the grounds are saturated during the bloom and pour steadily.
5) Dose is too low
If you’re using too little coffee for the amount of water, the brew can taste thin and overly acidic. Even if extraction is technically correct, the balance will feel off because there isn’t enough concentration to support sweetness and body.
Simple fix: Increase your dose slightly or reduce the water a touch. Keep the change small so you don’t swing from sour to bitter.
How to Fix Sour Coffee by Brew Method
Espresso
Sour espresso usually means the shot is running too fast. When water passes through the puck too quickly, it extracts acids before sweetness develops. This often shows up as a shot that finishes well under 25 seconds.
What to change: Grind slightly finer and check your yield. A typical starting point is a 1:2 ratio (for example, 18g in, 36g out) in around 25–30 seconds. If the shot is still sharp, slow it down a touch more. Make sure your puck prep is consistent, as uneven distribution can cause parts of the coffee to under-extract.
For a full step-by-step breakdown, see our guide on dialling in espresso at home.
Cafetière
In a cafetière, sourness usually means the coffee hasn’t had enough time or surface contact to extract properly. If the grind is too coarse or the brew time is too short, sweetness won’t develop to balance acidity.
What to change: Try a slightly finer grind and aim for around four minutes total brew time. Make sure all the grounds are fully saturated at the start, and give a gentle stir if needed to prevent dry pockets. After plunging, pour it out immediately rather than leaving it in the pot.
Pour Over
Sour pour over often shows up when the brew runs too quickly. If your total brew time is very short, or the water flows straight through, you’re likely under-extracting. Uneven pouring can also leave parts of the bed barely touched by water.
What to change: Grind a little finer and aim for a steady, controlled pour. Keep your water around 94-96°C and make sure all the grounds are properly saturated during the bloom. If your drawdown is very fast, adjust the grind slightly finer and test again.
How to Make Coffee Taste Sweeter
If your coffee tastes sour, the real goal isn’t just to remove sharpness. It’s to bring out sweetness. When extraction is balanced, sweetness naturally sits in the middle of the cup.
Grind slightly finer to increase extraction. Make sure your brew runs long enough for sweetness and body to develop. Check your ratio as well. If the brew is too diluted, sweetness won’t feel present even if extraction is correct.
Even agitation helps. Gentle stirring in a cafetière or consistent pouring in a pour-over keeps extraction uniform and prevents sharp, under-extracted pockets in the cup.
When grind, time, temperature and ratio are working together, sweetness shows up naturally. You shouldn’t have to chase it.
FAQs
Is sour coffee under-extracted?
Most of the time, yes. Sour coffee usually means the brew hasn’t extracted enough from the grounds. The brighter acids dissolve first, but sweetness and body develop later. If the brew stops too early, the cup tastes sharp and thin rather than balanced. Grinding slightly finer or brewing a little longer often corrects it.
Why does my espresso taste sour?
Sour espresso typically means the shot is running too fast. If water passes through the puck too quickly, it pulls acids but not enough sweetness. This often happens when the grind is too coarse or the dose is too low. Aim for a balanced extraction time and adjust your grind gradually.
Can light roast taste sour?
Light roast coffee preserves more natural acidity, so it can taste brighter than darker roasts. That brightness isn’t automatically a flaw. However, if it tastes sharp, hollow or thin, it may still be under-extracted. Proper brewing should reveal sweetness alongside acidity, not just sharpness.
Does water temperature affect sourness?
Yes. Water that’s too cool extracts more slowly and can lead to under-extraction. If your brew tastes sour and thin, try increasing your water temperature slightly within the recommended range. Small changes can make a noticeable difference.
Why does my coffee taste both sour and bitter?
This usually means uneven extraction. Some parts of the coffee bed are under-extracted, while others are over-extracted. The result is a confusing cup that tastes sharp and harsh at the same time. Improving grind consistency, even pouring, and proper puck preparation can help bring the brew back into balance.