Mash Bill Calculator

It calculates each grain's weight directly from the percentage you enter for that grain, without checking the other three against each other, so the Total Percentage figure exists purely as a manual sanity check — if it doesn't read 100%, your four percentages don't actually add up to your full grain bill, and you should adjust them before finalizing your recipe.

That threshold is set by U.S. federal regulations defining what can legally be labeled bourbon — corn's high starch content and mild, sweet flavor form bourbon's characteristic base, and the 51% minimum is a legal requirement, not a flavor recommendation, so a mash bill just under that threshold cannot be sold as bourbon regardless of how similar it tastes.

No — each grain's weight is calculated independently from its own percentage times the total grain weight, so changing corn percentage has zero effect on the calculated rye, malted barley, or wheat weights. If you want your mash bill percentages to still sum to 100% after adjusting one grain, you need to manually reduce one or more of the others to compensate.

It's a rough approximation based on typical grain starch content and conversion assumptions, not a measurement of your specific mash — real alcohol yield depends on your actual grains' starch levels, how efficiently your malted barley converts those starches to sugar, fermentation temperature, and yeast health. Use it as a ballpark planning figure and rely on a hydrometer reading of your actual wash for a real yield estimate.