Pearson Square Calculator
Tells you how much of two feeds to mix to hit a target crude protein — and tells you when the mix you're asking for is impossible.
Figures reviewed against university extension guidance · Last reviewed July 2026
- Feed 1 — 10% protein
- 82.86 lb
- 82.86% of the mix · 29 parts
- Feed 2 — 45% protein
- 17.14 lb
- 17.14% of the mix · 6 parts
- The mix comes out at
- 16% protein
- crude protein only — this is not a complete feed
A worked layer ration
Corn at 10% protein and soybean meal at 45%, mixed to a 16% layer ration, comes out at 82.86% corn and 17.14% soybean meal — about 82.86 lb of corn to 17.14 lb of meal in a 100 lb batch. Change any of the four numbers above to match what's actually in your shed.
How this works
Draw a square. Put your two feeds' protein percentages on the left corners and the protein you want in the middle. Subtract diagonally, ignoring the minus signs, and the numbers that fall out on the right are the parts of each feed. Divide each by the total and you have your proportions. That's the whole method, and it's older than every one of us.
Take Cornell Cooperative Extension's own example: corn at 10% protein, soybean meal at 45%, target 14%. The diagonals give 31 parts corn and 4 parts meal — 31 + 4 = 35 parts total, so 88.57% corn and 11.43% soybean meal. Cornell publishes exactly those figures, 88.57 and 11.43, and so does this page — the calculator is tested against their worked example and against N.C. Cooperative Extension's, so if our arithmetic ever drifted from theirs, the build would fail.
The one rule that trips people up is that your target must sit between your two feeds. Cornell states it directly: the value in the middle of the square must be intermediate between the two values on the left. Blending is averaging. Two feeds at 10% and 16% can produce anything from 10% to 16% and nothing else — ask for 20% and there is no ratio that gets you there, only a stronger ingredient. Most calculators quietly return a nonsense number here; this one tells you it can't be done.
What protein to aim for
Extension services agree on laying hens and part ways on growing birds. Both figures are below — where two land grant universities disagree, the range is the honest answer.
| Stage | Age | Penn State | Georgia |
|---|---|---|---|
| Chick starter | 0–8 weeks | 18–20% | 20% pullet · 22% broiler |
| Grower / developer | 8–18 weeks | 14–15% | 17% pullet · 20% broiler |
| Layer | 18+ weeks | 16–18% | 16–18% |
This does not make a complete feed
Read this before you mix anything you intend to feed exclusively. The Pearson square balances one nutrient. Hitting 16% protein says nothing whatsoever about calcium — which is what an eggshell is made of — nor about phosphorus, methionine, lysine, or a single vitamin. Oklahoma State Extension puts the risk plainly: it is best to use complete feeds not requiring supplementation with other ingredients, because relying on grains and other feed materials can cause an imbalance of nutrients and mineral or vitamin deficiencies, resulting in reduced growth, production or adverse health effects. A corn-and-soybean blend at exactly 16% protein will still fail a laying flock.
So what is this good for? Understanding what you already have — working out that your "16% layer feed" cut half-and-half with scratch is really feeding about 12%. Topping a ration up during a molt, when birds want more protein to rebuild feathers. Checking a feed-store blend's claim. Teaching yourself why the numbers on the bag matter. Those are all real uses. Replacing a formulated ration with two sacks and some arithmetic is not.
A worked example
Say you keep layers and want a 16% ration from corn (10% protein) and soybean meal (45%). Target minus the corn: 16 − 10 = 6 parts of meal. The meal minus the target: 45 − 16 = 29 parts of corn. That's 35 parts in total, so corn is 29 ÷ 35 = 82.86% and meal is 17.14%. For a 100 lb batch: 82.86 lb of corn and 17.14 lb of soybean meal, which delivers 16% protein exactly.
Then add your calcium source, your vitamin and mineral premix, and check your amino acids — because that 16% is one number out of a dozen that matter, and it's the easiest one.
Sources
The default feed values (corn 10% CP, soybean meal 45% CP) come from Cornell's own worked example. Real feeds vary by lot — the guaranteed analysis on your bag is the number that counts, which is why both are inputs.
- Cornell Cooperative Extension — Formulating Rations with Pearson Squares
- N.C. Cooperative Extension — The Pearson Square — the Tool for Balancing Rations
- Penn State Extension — Management Requirements for Laying Flocks
- University of Georgia Extension — Nutrition for the Backyard Flock (Circular 954)
- Oklahoma State University Extension — Backyard Flock Production (fact sheet ANSI-8202)
Frequently asked questions
- What is the Pearson square?
- A century-old bit of arithmetic for blending two feeds to a target nutrient level, usually crude protein. You write your two feeds on the left of a square, the protein you want in the middle, then subtract diagonally — the differences are the "parts" of each feed. It is the quickest way to answer "how much soybean meal do I add to my corn", and it is still taught by extension services because it takes ten seconds on paper.
- Will this give me a complete chicken feed?
- No, and this is the part worth reading twice. The Pearson square balances exactly one nutrient. Hitting 16% protein tells you nothing about calcium, phosphorus, methionine, lysine, or vitamins — and a laying hen needs all of them. Oklahoma State Extension is blunt about the risk: it is best to use complete feeds not requiring supplementation, because relying on grains and other feed materials can cause an imbalance of nutrients and mineral or vitamin deficiencies, showing up as reduced growth and production. Use this to understand a blend or to top up a ration, not to invent a diet from scratch.
- How do I use it for chicken feed?
- Take the protein figure off each bag's guaranteed analysis, put them in, and set the protein you want. Mixing corn at 10% with soybean meal at 45% to reach 16% gives you about 83% corn and 17% soybean meal — so a 100 lb batch is roughly 83 lb of corn and 17 lb of meal. Weigh it, do not scoop it; the whole point of the arithmetic is defeated by guessing at the proportions.
- Why won't it let me hit the protein I want?
- Because your target has to sit between your two feeds. Cornell Extension states the rule plainly: the value in the middle of the square must be intermediate between the two values on the left. Blending is averaging, so two feeds at 10% and 16% can only ever produce something between 10% and 16%. If you want 20%, no ratio will do it — you need a stronger protein source in the mix.
- What protein do my birds actually need?
- Extension services agree on layers and disagree on growers. Penn State Extension gives 18–20% for chick starter, 14–15% for a grower or developer to 18 weeks, and 16–18% for a layer ration. University of Georgia Extension runs higher on the growing birds — 20% for a pullet starter and 17% for a pullet grower — while giving the same 16–18% for layers. Where two extension services differ, treat the range as the honest answer rather than picking one to sound confident.
- Can I use it with more than two ingredients?
- Indirectly. The square handles two things at a time — both Cornell and NC State Extension note it is most effective with exactly two. The standard workaround is to combine your grains into one mix, work out that mix's average protein, then treat it as a single ingredient against your protein supplement. Beyond that you have left the world of paper arithmetic and want real least-cost formulation software.