# Top-down Brew: Hop IBU Percentage Calculator

## Purpose: To calculate the IBUs and IBU percentages from multiple hop additions

Original gravity (in specific gravity or degrees Plato)
Target volume (gallons or liters)

Hop data: Name, weight, alpha acid percentage, boil minutes (with comma separated values):

Hop #1:
Hop #2:
Hop #3:
Hop #4:
Hop #5:
Hop #6:
Hop #7:
Hop #8:
US units (gallons, ounces) Metric units (liters, grams)
← Click here when the data entry is done.

## Results

*** Waiting for results ***

## Notes

This calculator can take the basic values from standard recipes (weight, time, alpha acid percentage) and easily convert these to IBU percentages for use in a flex recipe.

The beer engine concise format is...

    h: name, ibu percentage, alpha acid percentage, boil time

IBU percentages are calculated from the IBUs contributed by each hop addiction divided by the total projected IBUs.

The IBU calculations are based upon the Tinseth formula. A small improvement upon the Tinseth formula is that aroma hops (defined as less than 2 minutes of boil) are assumed to have a utilization of 5%. The IBU calculations estimate boil volume and gravity for a 15% per hour boil off rate.

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This work is licensed under a Creative Commons Attribution 4.0 International License.