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Coffee Ratio Calculator

Calculates coffee and water amounts for filter, French press, AeroPress, espresso or cold brew, in either direction.

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Enter your figures and press Calculate.
In short Coffee Ratio Calculator is a free online tool on inputtesthub.com that calculates coffee and water amounts for filter, French press, AeroPress, espresso or cold brew, in either direction. It needs no account, no download and no payment, and there is no daily usage limit. Everything is processed inside your own browser, so the data you paste is never uploaded to a server.

How to use the Coffee Ratio Calculator

  1. Enter your figures in the input fields.
  2. The result updates as you type, together with the full working.
  3. Check the breakdown table to see exactly how the number was reached.

About the Coffee Ratio Calculator

The Coffee Ratio Calculator calculates coffee and water amounts for filter, French press, AeroPress, espresso or cold brew, in either direction. It runs as plain JavaScript inside the page, which means there is no upload step, no queue and no size limit imposed by a server — the only limit is your own device.

What people use it for

  • Scaling a recipe to the size of your carafe.
  • Working backwards from the coffee you have left.
  • Comparing strength across brew methods.

Details

Filter1:16.7
French press1:15
AeroPress1:14
Espresso1:2
Cold brew concentrate1:8

The maths behind it

This tool uses Coffee = water ÷ ratio, or water = coffee × ratio. One millilitre of water weighs one gram, so weight and volume are interchangeable. Every intermediate value is shown on screen, so the result can be checked by hand.

Adjust the grind before the ratio. Sour and thin means under-extracted — grind finer or brew longer. Bitter and harsh means over-extracted — grind coarser. Grind size changes extraction far more than a gram either way.

Frequently asked questions

Are there any usage caps on the Coffee Ratio Calculator?
There is no cost and no cap. The Coffee Ratio Calculator is not a demo of a paid product, so nothing is held back or watermarked.
Does anything I enter leave my computer?
No. The Coffee Ratio Calculator runs entirely in your browser using JavaScript. Your input never reaches inputtesthub.com or any third party — open your browser's Network tab while you use it and you will see no request go out.
What formula does the Coffee Ratio Calculator use?
It uses Coffee = water ÷ ratio, or water = coffee × ratio. One millilitre of water weighs one gram, so weight and volume are interchangeable. The full working is printed under the result, so you can follow every step rather than trusting a black box.
When would I actually need the Coffee Ratio Calculator?
Typical uses: scaling a recipe to the size of your carafe. Working backwards from the coffee you have left. Comparing strength across brew methods. It is built for exactly those cases rather than being a general-purpose tool with this bolted on.
Any caveats I should know about?
Adjust the grind before the ratio. Sour and thin means under-extracted — grind finer or brew longer. Bitter and harsh means over-extracted — grind coarser. Grind size changes extraction far more than a gram either way.
What are the reference figures here?
Filter is 1:16.7. French press is 1:15. AeroPress is 1:14. These are printed on the page itself, so you do not have to take them on trust.
Can I rely on this for exact work?
The calculation runs in double precision and the result is shown to ten significant figures, so converting a value and converting it back returns the original. What is displayed is rounded for readability; what is copied is not.

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