Grain moisture shrink calculator: weight lost when grain is dried.

By the Autowhat AI team · Updated 2 Nov 2026

What is grain moisture shrink?

When wet grain is dried, the water that leaves it takes weight with it. Moisture shrink is that weight loss, expressed as a percentage of the weight before drying. It matters whenever grain is bought, stored or dried on a weight basis: a lot weighed wet and sold dry will weigh less, and the difference is water, not missing grain. Knowing the expected shrink lets a buyer, a warehouse or a farmer check a drying or weight deduction instead of arguing about it.

The key idea is that the dry matter in the grain does not change during drying; only the water does. So the weight after drying is whatever weight keeps the same dry matter at the new, lower moisture percentage. Moisture here is on the wet basis, which is how moisture meters and trade specifications normally report it.

How it is calculated

With W the initial weight, M1 the initial moisture % and M2 the target moisture %:

• Weight after drying = W × (100 − M1) ÷ (100 − M2)
• Water removed = W − weight after drying
• Moisture shrink % = (M1 − M2) ÷ (100 − M2) × 100
• Shrink per point = shrink % ÷ (M1 − M2), which equals 100 ÷ (100 − M2)
• Handling loss = W × handling % ÷ 100 (a figure you set; the tool adds nothing by default)
• Total loss = water removed + handling loss; net weight = W − total loss

This is the same dry-matter relationship used in the Canadian Grain Commission’s Order Respecting the Calculation of the Moisture Shrinkage for Grain (SOR/2018-176), which sets the formula for grain dried at licensed elevators in Canada, and in the Purdue, Iowa State and Wisconsin extension publication NCH-61, Grain Shrinkage Due to Drying, which also explains handling loss and “shrink factors”. Neither is an Indian rule. In India, a buyer’s or agency’s own terms decide whether and how a moisture or weight deduction applies; check them, and the specification in force on the Food Corporation of India website for procurement moisture limits. This page is illustrative; confirm with your adviser / the official source before settling a payment.

Worked example (illustrative)

Suppose 1,000 kg of wheat is weighed at 17% moisture and dried to 12%.

1. Dry matter stays the same: 1,000 × (100 − 17) = 83,000.
2. Weight after drying = 83,000 ÷ (100 − 12) = 943.18 kg.
3. Water removed = 1,000 − 943.18 = 56.82 kg.
4. Moisture shrink = (17 − 12) ÷ 88 × 100 = 5.68%, or about 1.136% for each point of moisture removed.
5. If the parties had agreed a 0.5% handling loss, that adds 5 kg, so total loss is 61.82 kg and net weight is 938.18 kg.

The numbers are for illustration only; the handling figure is an assumption you would replace with the one in your own agreement.

Why shrink is more than the drop in moisture

Taking 5 points of moisture out removed 5.68% of the weight, not 5%. That is because the moisture percentage is measured against the total weight, and the total weight falls as water leaves. Each point removed is a slightly larger share of what is left. The drier the target, the larger the shrink per point: 100 ÷ (100 − M2) is about 1.136 at 12% and about 1.163 at 14%. Using a flat “1% per point” rule understates the loss.

Getting a fair number

• Use a calibrated moisture meter and a representative sample; a single handful from the top of a bag is not the lot.
• Record which moisture basis is used (wet basis is standard in trade).
• Agree any handling or invisible-loss allowance in writing before drying, not after.
• Weigh on the same scale before and after where you can, so scale differences are not mistaken for shrink.

Where GrainGrade fits

A moisture reading is one part of judging a lot; the other is its physical condition. GrainGrade, Autowhat’s app now in development for a grain quality check at the mill gate, counts and measures grain from a phone photo and grades the visible defects. It does not measure moisture: a camera cannot see it, so moisture is entered from a meter reading. For the full specification, read FCI FAQ wheat specification explained, and for the limits of image-based checks see what a wheat photo cannot tell you.

See it on your own data. GrainGrade — Wheat graded from a photo. Book a 30-minute working session with an engineer.

General guidance, current as of the date above. Figures and examples are illustrative unless a source is linked.