Water Temperature, Volume and Ratio for Coffee
On this page we’ll detail how to determine the right temperature and ratios to use to develop a high quality cup of coffee so you fully understand the impact of water temperature, water types, and the so-called “golden ratio”.
A brew ratio refers to the proportion of coffee and water found in each serving of coffee.
The larger number referred to in the ratio always refers to water, since that the volume of water will always exceed the volume of coffee.
Often the coffee to water ratio will be expressed with two different measurement units. We use grams for coffee and milliliters for water.
So a ratio of 15:100 would mean 15 grams of coffee (the smaller number) to 100 milliliters of water (the larger number).
The Golden Ratio
According to the SCAA the recommended coffee to water ratio - the “golden ratio” - should be roughly 1:18. This means for every 55 grams of coffee you would use 1 liter of water1.
Keep in mind that in many cases you may find you need ½ the recommended amount of coffee, depending on the brewing method.
Note that coffee measurements are usually most helpful when they are done by weight vs volume. The issue with measuring volume is that coffee beans will not have a universally consistent size or density.
Espresso shots are tricky. Some experts disagree about the optimal weight of coffee that should be present and differences in the type of equipment used can also mean other nuances need to be considered when determining the best ratio.
Generally speaking most would agree that 7-8 grams (~0.28 ounces) of coffee should be used for a single shot of espresso or 15 grams (0.52 ounces) for a double shot.
Keep in mind this is widely considered to be the more traditional European style express and many specialty coffee sellers will choose their own ratios for espresso. The Third Wave Coffee movement tends to recommend a volume of 18 - 20 grams of coffee for double espresso shots.
Coffee and Water
Water makes up 98% to 99% of most any cup of coffee so it should be no surprise that it’s one of the more important components.
The quality of the coffee is largely going to be determined by the amount, the type, and the temperature of the water.
The minerals in water are key components of the taste of coffee, and for that reason distilled water, which has all the minerals extracted, is never used in the process of brewing. Mineral water also has a high acidity level that over time can corrode and damage coffee equipment.
Also, it’s recommended that hard water is avoided because hard water contains minerals that can coat plumbing with calcium deposits and form blockages.
It might be tempting to take hard water and soften it with tablets but that’s also not advisable as water softening tablets contain sodium that can eventually turn gelatinous and clog up the equipment.
Types of Water
Filtered water is the best choice for making coffee.
Chemicals and sediment are removed from filtered water though carafe or charcoal filters but still retain the important materials once filtered.
Filtered water is the ideal choice for coffee making, because carafe, sink-based or charcoal filters remove chemicals and sediment while retaining important minerals.
You can also use bottled spring water as long as it contains between 50 to 150 parts mineral content. The mineral content in the water should not exceed 300 ppm (parts per million).
Because hot water is responsible for the dissolution of soluble solids in the ground coffee, ensuring the right temperature is a key part of ensuring the proper flavor and aroma is developed.
Generally speaking the proper temperature for brewing coffee will be somewhere between 196°F (91°C) - 205°F (96°C). While you want to avoid bringing the coffee to a boiling temperature of 212°F (100°C) , coming as close as possible to the higher range of 205°F is recommended.
If the water comes in below 196°F (91°C) it will likely under extract the coffee and make for a very weak serving.
All that said, a very dark roast will have an easier time handling brewing at lower temperatures which is sometimes good to know if coffee is being brewed with cheaper equipment that has difficulty heating up the water.
Did You Know?
If you’ve ever wondered about the impact of temperature on coffee, consider the extreme difference of hot coffee vs cold brew. Cold brew coffee has the advantage of being less acidic and is easier to digest. Conversely, hot coffee is more likely to make people feel comfortable and warm interpersonally2
Does water temperature matter in coffee?
Yes, this is because the hotter the temperature the faster the extraction. The extraction shapes the flavor and aroma that is brought out in the coffee and when it happens very quickly it becomes more difficult to control - which makes it harder to craft a balanced coffee brew.
Does boiling water ruin coffee?
Boiled water has two disadvantages.
First, it hastens the speed of extraction and will often result in an over extracted and bitter cup of coffee. The other drawback is that it can unnecessarily agitate the coffee grounds (depending on the brewing method) and possibly lead to unbalanced extraction.