Grain Moisture Adjustment Calculator

Grain leaves the field carrying water that nobody wants to buy. A load of corn that reads 25% moisture on the harvest tester is a quarter water by weight, and that water evaporates during drying and storage. Elevators know this, so they pay on a standard moisture — commonly around 15% for corn — and they dock or dry anything wetter. That is why a scale ticket showing 56,000 lb of wet corn does not tell you how much grain you actually have to sell.

This calculator settles that question. Give it the wet weight off the scale, the moisture you measured, and the moisture you are pricing against, and it returns the equivalent weight at that target moisture. It also reports shrink — the weight that disappears as water is driven off. The math is crop-agnostic: corn, soybeans, wheat, barley, and canola all follow the same dry-matter accounting, so one tool covers the whole harvest as long as moisture is read on a wet basis and your weight unit stays consistent.

Plain-text formula: adjustedWeight = wetWeight × (100 − measuredMoisturePct) ÷ (100 − targetMoisturePct); shrinkWeight = wetWeight − adjustedWeight; shrinkPct = 100 × shrinkWeight ÷ wetWeight. Moisture percentages are on a wet basis.

How to use this calculator

There are three boxes to fill in, and all of them come off things you already handle at harvest. In Wet Grain Weight, put the number from the scale ticket — the load exactly as it came off the field, water and all. In Measured Moisture, enter the reading from your harvest tester or the probe at the pit as a plain percent like 20 or 18.5, not a decimal. In Target Moisture, enter the moisture you want to compare against: usually the buyer's contract standard (about 15% for corn) or the level you plan to store at.

Press Adjust Weight and the result line shows three things: the equivalent weight at your target moisture, the shrink (both as a weight and as a percent of the original load), and the pounds — or kilograms — of dry matter riding in the load. The weight comes back in whatever unit you typed in the first box; nothing is assumed about pounds versus kilos. If you enter a target that is wetter than what you measured, the tool still answers but labels the change a "difference" rather than shrink, because you are adding notional water back rather than driving it off.

Why wet weight lies about yield

Field corn often comes in at 22–28% moisture while the buyer pays on roughly 15%. Line up two loads by scale weight alone and the wetter one looks like the better field — even when it holds no more actual grain than the drier one. The starch, protein, and oil, the part you are really selling, is the dry matter; everything else is water that will leave. Convert both loads to a common moisture and the comparison finally becomes honest, which is what you want when ranking hybrids, deciding whether to dry on-farm or deliver wet, and checking that a bin will keep through the season.

The whole method rests on how moisture is defined. This tool uses wet-basis moisture, the convention in grain marketing, where moisture is the mass of water divided by the total mass of water plus dry matter:

A 100 kg sample holding 15 kg of water reads 15% moisture and carries 85 kg of dry matter. Drying pulls off water while leaving that dry matter behind, so the job of moisture adjustment is to hold the dry matter fixed and recompute the total weight at a new water fraction.

The formula, and where shrink comes from

Write the wet weight and measured moisture as W_w and M_w, the target moisture as M_d, and the answer — the weight at the target moisture — as W_d.

The dry-matter fraction of the load is (100 − M_w) %, and the dry matter fraction at the target moisture is (100 − M_d) %. Since drying does not create or destroy dry matter, the pounds of dry matter on each side must match:

Solve that for W_d and you get the one line the calculator runs:

W_d = W_w × (100 − M_w) / (100 − M_d)

It is just the original weight scaled by the ratio of the two dry-matter fractions, so the grain stays constant and only the water moves. Shrink is then the weight that left — the gap between what you weighed and what you have at the target moisture — reported both as a raw weight, W_shrink = W_w − W_d, and as a share of the load, S = 100 × W_shrink / W_w. That percentage is a clean baseline for the physical water loss; any drying fee or "management shrink" an elevator adds on top is a separate line item.

Worked example: a corn load from 20% to 15%

Take a truckload of corn weighing 56,000 lb that tested at 20.0% moisture, and price it against the buyer's 15.0% standard. The dry-matter fractions are 100 − 20.0 = 80.0% at the scale and 100 − 15.0 = 85.0% at the target. Feed those into the formula:

W_d = 56,000 × (80.0 / 85.0) = 56,000 × 0.94118 ≈ 52,706 lb

So drying from 20% to 15% leaves roughly 52,700 lb of saleable corn, before any handling loss or quality discount. The shrink is 56,000 − 52,706 ≈ 3,294 lb, or 100 × 3,294 / 56,000 ≈ 5.9% of the load — that 5.9% was water you were never going to be paid for at 15% moisture. The dry matter itself, 56,000 × 0.80 = 44,800 lb, never budged; it is simply carried by less water at the end.

Typical target moisture by crop

Target moisture depends on the crop, how long you intend to store, and the buyer's policy. The ranges below are common across many regions, but treat them as a starting point and confirm your local standards:

Use the buyer’s standard or your target storage moisture as the Target Moisture (%) in the calculator to see how much saleable grain you can expect from a wet load.

Reading the result and getting the inputs right

The adjusted weight is what you effectively have at the target moisture, and it is the figure to lean on when you convert every load to one basis before comparing fields, hybrids, or treatments, when you estimate saleable bushels at an elevator's standard to weigh contract options, and when you decide whether to dry on-farm or hand a wet load to the elevator's dryer. If the adjusted weight comes back far lower than you expected, the usual culprit is a moisture entered wrong — check that both moisture values are percents on a wet basis and that the target is realistic for the crop.

Weight is unit-agnostic: pounds, kilograms, metric tons, or short tons all work, and the answer returns in whatever unit you entered. Keep it consistent across the load. If you track grain in bushels, convert to weight first with a test weight — about 56 lb/bu for corn, 60 lb/bu for wheat and soybeans, or the figure measured on your own farm — because moisture is a mass concept and this tool works on weight, not volume. And enter moisture as a percent, not a decimal: 18.5 for 18.5% moisture, never 0.185.

Questions growers actually ask

How do I choose a target moisture? Use the standard written into your grain contract, or a moisture that stores safely for how long you plan to hold it in your climate. Extension bulletins and your elevator's posted policy are the best references for typical targets by crop and region.

What exactly is grain shrink? It is the drop in total weight as grain dries from a higher moisture to a lower one, and most of it is simply water leaving. Elevators sometimes tack on an extra "management shrink" or handling charge, which is a business fee rather than physical water loss.

Does this include elevator shrink policies or drying fees? No. The calculator models only the physical shrink from removing water, based on the moisture percentages you enter. It does not apply any additional shrink factor, service fee, or price discount a particular buyer might use.

Can I use it for crops other than corn? Yes. As long as moisture is on a wet basis and you pick an appropriate target for the crop, the same formula handles soybeans, wheat, barley, canola, and most other grains and oilseeds.

What the model assumes, and what it leaves out

The math here is deliberately simple, and simple models earn their keep only when you know their edges. This one assumes moisture is reported on a wet basis; if your figures are dry-basis, convert them first. It assumes dry matter is conserved — that drying removes water and nothing else — when in practice a little is always lost to fines, handling, and damage. It ignores foreign material and quality factors: no test-weight change, damage discount, or grading adjustment enters the number. And it knows nothing of elevator-specific policies, so the physical shrink it reports can differ from the shrink and drying charges a buyer actually bills. Treat the output as planning and comparison guidance; for settlement, rely on the official scale ticket and the terms in your contract. The formula follows the standard wet-basis drying and shrink calculations published by land-grant extension services, which are the place to go for crop- and region-specific detail.