Grain Moisture Adjustment Calculator

Introduction: what a wet scale ticket does not tell you

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 splits the loss into its two real parts: water shrink, the weight that physically leaves as vapour, and handling shrink, the flat percentage many buyers deduct on top to cover fines, dust and dry-matter lost through the dryer and the legs. 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.

Because settlement is written in bushels rather than pounds, the calculator also converts the answer using a test weight you supply (56 lb/bu for corn, 60 lb/bu for wheat and soybeans, 50 lb/bu for canola) and, if you give it a price, reports what the load is worth once shrink has been taken out. Those three numbers — adjusted weight, settlement bushels and value — are the ones that actually decide whether to dry on the farm, deliver wet and take the dock, or hold the load in a bin.

Plain-text formula: adjustedWeight = wetWeight × (100 − measuredMoisturePct) ÷ (100 − targetMoisturePct); waterShrink = wetWeight − adjustedWeight; handlingShrink = adjustedWeight × handlingPct ÷ 100; settlementWeight = adjustedWeight − handlingShrink; bushels = settlementWeight ÷ testWeightLbPerBu. Moisture percentages are on a wet basis.

How to use the grain moisture adjustment calculator

The first three boxes come straight 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 — and use the unit selector next to it to say whether that figure is pounds, kilograms, metric tonnes or short tons. 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.

Three more boxes turn the physics into a settlement figure. Handling shrink is the flat percentage a buyer deducts on top of water loss; 0.5% is the figure most published drying tables use, and 0 turns the deduction off if you only want the physical answer. Test weight is the pounds in a bushel of your crop, which the tool needs before it can quote bushels. Price per bushel is optional; leave it at zero and the value line is simply omitted.

Press Adjust weight and shrink and the result panel breaks the load into adjusted weight at your target, water shrink, handling shrink, total shrink, settlement weight, moisture shrink factor, dry matter, settlement bushels and — when you supplied a price — gross value. The weight figures come back in the unit you selected; bushels are always computed through pounds. 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. Press Reset calculator to return every field to its default corn scenario.

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 and the basis USDA's Federal Grain Inspection Service certifies against, 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. Dry-basis moisture, which divides water by dry matter instead of by total weight, is common in engineering literature and always reads higher; mixing the two conventions is the single most common way to get a badly wrong shrink figure.

Formula for wet-to-dry weight, shrink factor and total shrink

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:

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. Water 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.

Grain buyers rarely write it that way. They quote a moisture shrink factor instead: the percent of the starting weight lost per point of moisture removed, which depends only on the final moisture.

At a 15.0% final moisture that is 100 / 85 = 1.176, and at 15.5% it is 100 / 84.5 = 1.183 — the familiar "1.18" of the drying tables. Multiply the factor by the number of points removed and you get the same water shrink percent the ratio formula gives. Buyers then add a flat handling shrink H, usually 0.5%, for fines, dust and dry matter genuinely lost in the dryer and the handling legs, so the number that actually appears on a settlement sheet is a total:

Finally, settlement is written in bushels, so the calculator divides the weight left after both deductions by the crop's test weight T in pounds per bushel:

Worked example: a 56,000 lb 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 with the usual 0.5% handling shrink, 56 lb/bu test weight and a cash bid of $4.30 per bushel.

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 ≈ 52,705.88 lb

So drying from 20% to 15% leaves roughly 52,706 lb of grain on a 15% basis. The water shrink is 56,000 − 52,706 = 3,294 lb, or 100 × 3,294 / 56,000 ≈ 5.88% of the load — water you were never going to be paid for at 15% moisture. Checking that against the shrink factor: 5 points removed × 1.176 = 5.88%, the same answer by the buyer's arithmetic.

Handling shrink then takes 0.5% of the adjusted weight, 52,705.88 × 0.005 ≈ 263.53 lb, leaving a settlement weight of about 52,442.35 lb. Total shrink is therefore 3,557.65 lb, or 6.35% of the wet ticket. Divide by the 56 lb/bu test weight and you are settling on 936.5 bushels, worth 936.5 × $4.30 ≈ $4,027 gross before drying charges. The dry matter itself, 56,000 × 0.80 = 44,800 lb, never budged; it is simply carried by less water at the end, minus the small amount that genuinely left as fines.

Run the same load the other way to see why over-drying hurts. Dry it to 13.0% instead of 15.0% and W_d = 56,000 × (80.0 / 87.0) ≈ 51,494 lb — about 1,212 lb, or 21.6 bushels, less than the 15% figure. The elevator will not pay you for water you removed below its standard, so those 21.6 bushels, roughly $93 at $4.30, are gone along with the extra fuel it took to drive them off.

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, and set the test weight from the same row, to see how much saleable grain a wet load really represents.

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-flexible: pounds, kilograms, metric tonnes and short tons are all accepted, and the weight answers return in whatever unit you selected while bushels are always computed through pounds. Keep the unit consistent across a load. If you track grain in bushels already, 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.

One number deserves particular care. Handling shrink is a policy input, not physics, and buyers differ: some publish 0.5%, some fold a larger figure into a drying table, and some charge a per-point drying fee instead. Iowa State work on measured handling losses found roughly 0.22% to 1.71% on farm and 0.64% to 1.33% through commercial systems, so 0.5% is a reasonable default rather than a law. If you are checking a settlement sheet, use the number your buyer actually publishes.

Questions growers actually ask

Limitations and assumptions of this shrink model

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 by the water-loss step — that drying removes water and nothing else — and puts every other loss into the single handling-shrink percent you supply, which is a blunt instrument compared with what actually happens in a dryer. It ignores foreign material and quality factors: no test-weight change, damage discount, heat-damage penalty or grading adjustment enters the number, and severe over-drying really does lower test weight and stress-crack the kernels in ways this model cannot see.

It also knows nothing of elevator-specific policies. Real settlement sheets apply a published discount schedule per point of moisture, a per-bushel drying charge, or a proprietary drying table that already bundles shrink and fee together, so the physical shrink reported here can differ from the money a buyer actually deducts. The value line is a plain multiplication of settlement bushels by the price you type; it contains no basis adjustment, no futures move and no delivery cost. Treat the output as planning and comparison guidance; for settlement, rely on the official scale ticket and the terms in your contract.

Finally, the tool is arithmetic, not agronomy. It will not tell you whether a bin will keep, which depends on temperature, aeration and time as much as on moisture, and it will not tell you whether drying is worth the propane, which depends on your dryer's efficiency and the moisture discount schedule you face. Those are decisions the numbers here support rather than replace.

Sources checked: the wet-to-dry weight formula and its worked example come from Purdue University Extension, R. L. Nielsen, Converting Wet Corn Weight to Dry Corn Weight (Pest&Crop newsletter). The moisture shrink factor 100 ÷ (100 − final moisture), the "total shrink = moisture shrink + handling loss" structure, the customary 0.5% handling deduction and the measured 0.22–1.71% on-farm and 0.64–1.33% commercial handling-loss ranges come from Pioneer agronomy, How to Determine Corn Moisture Shrink and Total Shrink, citing Iowa State University research. The 56,000 lb / 20% / 44,800 lb dry-matter example is worked the same way in Iowa State University Extension Ag Decision Maker, Corn Drying and Shrink Comparison (A2-32). Wet-basis moisture is the basis certified by USDA Agricultural Marketing Service, Federal Grain Inspection Service, Grain Moisture Handbook. Test weights per bushel follow the USDA Grain Inspection Handbook, Book II.