Butcher Shop: Fat To Add For A Target Sausage Blend

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Sausage is a percentage, not a feel. If you have 40 pounds of 90/10 trim and the recipe wants 25% fat, the question is not “how much fat looks right” — it is a single algebraic answer, and the spreadsheet gives it before the grinder turns.

Quick formula: The pounds of pure fat that hit the target:

=ROUND(B2*(D2-C2)/(1-D2),1)

40 lb of 90/10 trim needs exactly 8 lb of back fat to land on a 25% blend.

Functions used (tap for the full reference guide):

ROUND PRODUCT

The example

Three batches, each starting from a different trim and aiming at a different house blend.

	A	B	C	D	E
1	Batch	Trim lb	Trim fat %	Target fat %	Fat to add lb
2	Breakfast	40	10%	25%	8.0
3	Italian	60	15%	30%	12.9
4	Lean chicken	25	5%	20%	4.7

The formula

The algebra behind the column:

=ROUND(B2*(D2-C2)/(1-D2),1) // trim lb x fat gap, / the lean share of the target, to a tenth

How it works

Why the denominator is 1-Target and not 1:

Adding fat raises the fat pounds and the total pounds at the same time, so you cannot just multiply the trim by the gap.
D2-C2 is the gap you have to close — 25% target minus 10% already there is 15 points.
/(1-D2) corrects for the growing batch. At a 25% target, only 75% of the finished weight is lean, and the lean weight is fixed.
ROUND(...,1) to a tenth of a pound, which is what a shop scale reads anyway.

Add the result to the trim weight to get finished batch weight, and divide by your case pack to get the case count — the same batch sheet then drives the label run.

Try it: interactive demo

Interactive

Enter the trim weight, the fat already in the trim, and the blend you are aiming at.

Trim pounds

Trim fat % (0.10 = 10%)

Target fat % (0.25 = 25%)

Variations

Finished batch weight

Trim plus the fat you just calculated is what comes off the grinder.

=B2+ROUND(B2*(D2-C2)/(1-D2),1)

Blending two trims instead of pure fat

When the fat source is itself a trim, replace the 1 with that trim's fat share.

=ROUND(B2*(D2-C2)/(0.85-D2),1)

Pitfalls & errors

This assumes the added fat is essentially pure. Back fat is close; 50/50 trim is not, and using this formula for it will leave the batch lean.

Enter the percentages as real percentages (0.25, formatted as 25%), not as the number 25. A 25 in the target cell makes 1-D2 negative and the answer nonsense.

Labelling is a legal claim in most jurisdictions. The calculated blend is a target — verify the finished product before a package says 80/20.

Practice workbook

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Download the free Butcher Shop: Fat To Add For A Target Sausage Blend practice workbook

Edit the yellow trim, trim-fat, and target cells; the fat to add recalculates.

Frequently asked questions

How do I know the fat percentage of my trim?

Either from the supplier's spec on the box (81/19, 90/10) or from a lean-point test on a sample. If you grind your own trim from primal breakdown, run one batch through a lab test and use that as the house number for that cut.

What if I have to hit a target using two trims?

Use the second variation: replace the 1 in the denominator with the fat share of the fattier trim. The formula then tells you how many pounds of that trim to add rather than pounds of pure fat.

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Function references: ROUND PRODUCT