# 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)

Field order: Selection hop and alpha acid, weight (oz or grams), boil time in minutes

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

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## Notes

This calculator converts the basic values from standard recipes (weight, time, alpha acid percentage) into IBU percentages for use in a beer engine recipe.

The beer engine formatting is...

    hop: name, IBU percentage, alpha acid percentage, boil time in minutes

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.