To estimate standing hay tonnage, clip six to ten 1-square-foot samples at your mower's cutting height, dry them, and multiply average dry grams by 96 for pounds of dry matter per acre. Take off 15 to 20 percent for field losses, divide by 0.85 to add baling moisture back, multiply by mapped acres, and divide by weighed bale weight.
The hay standing in the field is not the hay you will put in the barn. Every published method, whether it is clipping, a height rule or a plate meter, tells you how many pounds of dry matter are standing on an acre. Getting from that to a bale count takes three more corrections, and most guides stop before the first one. That gap is where a "should be 90 bales" field turns into 66, and where a standing-hay deal gets priced on hay that never reaches the wagon.
This guide chains it together, mower to bale, with a worked example on a 38-acre field. Use it to decide whether a thin cutting is worth the fuel, to price hay bought or sold standing, or to plan next season.
Four things sit between the standing crop and the bale count:
Skip one and the error carries straight through to your answer.
Clip-and-weigh is the reference method. Mississippi State Extension's forage inventory guide (Pub 2458) puts it plainly: clipping and weighing a known area "is the most accurate method but requires you to dry and weigh clipped forage."
What you need: a frame of known area, hand shears or a battery grass shear, paper bags, a marker, and a kitchen scale that reads in grams.
Split a variable field. Eight square feet is a sliver of 38 acres, and the bigger error source is the field, not the scale. If the bottom ground is thick and the hilltop is thin, clip each zone separately, estimate each, and weight them by acres. More clips beat a better scale every time.
Hay fields are not pastures, and the tools differ. Our pasture stocking rate calculator guide covers the grazing stick and hoop clips for grazed ground. This guide is for a stand you plan to cut.
Weigh each clipped sample green, right away, before it wilts. Then dry a subsample to find its dry matter percentage. Mississippi State's microwave procedure:
Stay at the microwave the whole time. Dry forage can scorch or catch fire, and MSU warns about damaging the oven. Use an old one, not the one in the house.
Dry matter % = dry weight ÷ wet weight x 100. Multiply each sample's green weight by that percentage to get its dry grams. For moisture meters, the Koster tester and baling moisture, see our hay moisture testing guide.
An acre is 43,560 square feet and a pound is 453.6 grams. Divide one by the other and you get 96. So:
Average dry grams per square foot x 96 = pounds of dry matter per acre.
| Sampling frame | Area | Multiply average dry grams by |
|---|---|---|
| 1 x 1 ft square | 1 sq ft | 96 |
| 2 sq ft frame | 2 sq ft | 48 |
| 4 sq ft frame | 4 sq ft | 24 |
| UF ring (1/10,000 acre) | 4.36 sq ft | 22 (or ounces x 625) |
UF's own example shows why this matters for the "should I even cut it?" call. Six rings averaged 1.0167 ounces dry at a 7.21-inch average height. That works out to 635 pounds of dry matter per acre, or 747 pounds of hay per acre at 15 percent moisture. (The current UF web page prints 700; its own bale counts only work with 747, which is what the archived PDF shows.) That is less than one 900-pound bale per acre. UF's verdict: the field "would be better used for grazing or should be allowed to rest and grow more before harvesting."
Yes, for a go or no-go decision. Not for pricing a sale. The two most-cited height rules disagree by nearly double.
Run both on a 26-inch alfalfa stand: 26 x 126 = 3,276 lb of dry matter per acre, or 26 x 225 = 5,850 lb. More than a ton apart on the same stand. The lesson is not that one rule is right, but that height is a screen, not a scale.
If you use height at all, count stems first. Toss the same 1-square-foot frame and count alfalfa stems inside it. UW defines a stand averaging 55 stems per square foot as "not being limited." Below that, skip the height rule and clip.
Rising plate meters are out for hay. Kentucky's AGR-277 says plate meters "are designed to estimate yield on pastures at a vegetative growth stage" and are "not practical" on stands full of seedheads, which is exactly what a hayfield at cutting looks like. Our pasture management technology guide covers plate meters and satellite biomass where they do fit.
New Mexico State's Circular 668 collects the standard alfalfa loss figures (adapted from Rotz and Muck, 1994, and Rotz, 2005). These are dry matter losses:
| Step | Range | Average |
|---|---|---|
| Respiration while curing | 1-7% | 4% |
| Mowing and conditioning | 1-4% | 2% |
| Tedding | 2-8% | 3% |
| Raking | 1-20% | 5% |
| Baling, small square | 2-6% | 4% |
| Baling, round | 3-9% | 6% |
| Baling, large square | 1-4% | 3% |
| Rain on the windrow, 0.2 / 1 / 2 inches | 3-7 / 7-27 / 12-50% | 5 / 17 / 30% |
Add the averages for your system and you get a planning factor:
So standing dry matter x 0.80 to 0.85 is a fair estimate of baled dry matter. One inch of rain on the windrow takes off roughly another 17 percent. These numbers are alfalfa-based, and alfalfa sheds leaves worse than grass, so treat them as the cautious end. They are also ranges, not measurements. Raking alone runs from 1 to 20 percent, which is why rake setup matters; our guide to GPS-guided tedders and rakes covers it.
Three steps finish the chain.
1. Add the water back. Hay baled at 15 percent moisture is 85 percent dry matter, so divide baled dry matter by 0.85 to get pounds of hay. That 15 percent is a convention. USDA NASS reports hay at 13 percent moisture (0.87 dry matter), and hay baled at 18 percent weighs more per ton of feed. If you sell by weight, test moisture.
2. Multiply by the real acres. Your tons per acre is only half the answer. On a hayfield that follows a creek, wraps a draw or loses its corners to a pivot, guessed acres can be off more than your clip. Draw the field in our free Field Boundary & Input Calculator to get mapped acres, then multiply. It measures acreage and figures seed and fertilizer totals; it does not estimate yield, so the tons per acre still come from your clips. Our guide to calculating acreage on odd-shaped fields walks through it.
3. Divide by what your bales actually weigh. Weigh three bales from your own baler on a certified scale, or weigh one loaded wagon or truck and divide by the bale count. UW-Madison's Kevin Jarek says weighing at least one load "will significantly improve the yield estimate accuracy." UF says round bales "often weigh between 700-900 pounds." That range alone is a 25 percent spread.
No scale? Use the University of Missouri density method as a range, not a point. MU's Rob Kallenbach puts round bales at 9 to 12 pounds of dry matter per cubic foot, so a 5 x 5 bale (about 98 cubic feet) holds anywhere from about 880 to nearly 1,200 pounds of feed. A 4-wide x 5-tall bale at 9 pounds is about 710 pounds of dry matter.
Watch the basis. A scale weighs hay, water included. The density table gives dry matter. Divide hay by hay, or dry matter by dry matter. Mixing the two is the most common way a careful estimate goes wrong.
Once the hay is down, a baler monitor with bale weighing gives you the after-the-fact check on your estimate.
A 38-acre grass hay field, round bales, no tedder, mower set at 3 inches.
Same field, same clips, a 15-bale swing from bale weight alone. Here is how far the count moves with losses and bale weight:
| Field losses | Hay (lb) | 800-lb bales | 900-lb bales | 1,000-lb bales | 1,100-lb bales |
|---|---|---|---|---|---|
| 15% | 76,600 | 96 | 85 | 77 | 70 |
| 17% | 74,800 | 94 | 83 | 75 | 68 |
| 20% | 72,100 | 90 | 80 | 72 | 66 |
| 17% + 1 in of rain (34%) | 59,500 | 74 | 66 | 59 | 54 |
Run it on a dry matter basis with the MU density range instead: 2,016 x 0.83 x 38 = about 63,600 lb of baled dry matter. That is 72 loose 5 x 5 bales at 880 lb of dry matter, or 54 tight ones near 1,180 lb. Bale density moves the count more than field losses do. Weigh your bales.
Check your estimate against what fields actually make. USDA NASS's Crop Production 2025 Summary (January 2026) gives season totals, all cuttings combined, in tons of dry hay per acre:
| Alfalfa and alfalfa mixtures, 2025 | All other hay, 2025 | |
|---|---|---|
| United States | 3.42 | 2.09 |
| Washington | 5.00 | 2.40 |
| Oregon | 4.70 | 2.80 |
| Idaho | 4.10 | 2.20 |
Split them by cutting. UW-Madison's on-farm alfalfa data puts the first cutting at about 46 percent of the season in a 3-cut system, 36 percent in a 4-cut system and 32 percent in a 5-cut system. As a rough check, 5.0 tons x 36 percent is about 1.8 tons of hay per acre for a first cutting in a 4-cut Washington system. (That applies Wisconsin's split to Washington's average, so it is a sanity check, not a forecast.)
The worked example lands about 1 ton of hay per acre on one grass cutting, which fits inside a 2.1 to 2.8 ton season. If your clips say 5 tons per acre on a single cutting, something went wrong. Check that you clipped at mower height, that you used dry weight, and that you used the right multiplier for your frame.
Worth cutting? UF frames the question directly: "There must be enough material in the field to justify the cost of using harvesting equipment (i.e., purchase cost, rental cost, fuel, and labor); otherwise, the area should be grazed." Put your bale estimate next to what it costs you per acre to mow, rake, bale and haul. If the bales don't cover it, graze it or let it grow.
Selling or buying hay standing? UW-Madison's method (Jarek, 2023) is a sound starting point for both sides:
Use current prices, not old ones. The UW-Madison Hay Market Report and USDA AMS hay reports are updated regularly.
Clip at cutting height, not at the dirt. Dry the sample. Multiply by 96. Take off 15 to 20 percent for field losses, add the water back, and multiply by acres you have actually measured. Then divide by a bale weight you got from a scale, not a guess.
Before next season's first cutting, draw your hayfields once in the Field Boundary & Input Calculator and save the acres. Then the only number left to find in June is the one in the frame.
Clip six to ten 1-square-foot samples at the height your mower will cut, dry them, and average the dry weights in grams. Multiply by 96 to get pounds of dry matter per acre. For a bale count, take off 15 to 20 percent for mowing, raking and baling losses, divide by 0.85 for baling moisture, multiply by field acres, and divide by your weighed bale weight.
Multiply dry grams per square foot by 96. An acre is 43,560 square feet and a pound is 453.6 grams, and 43,560 divided by 453.6 is 96. For a 2-square-foot frame, multiply by 48; for 4 square feet, by 24. Use dry weight, not green weight, or the answer will be inflated by all the water in fresh forage.
For alfalfa in a normal dry-hay system, plan on about 15 to 20 percent of dry matter. New Mexico State's averages are 4 percent respiration, 2 percent mowing, 3 percent tedding, 5 percent raking and 3 to 6 percent baling depending on bale type. One inch of rain on the windrow adds about 17 percent more. Grass sheds fewer leaves, so it usually loses less.
It depends on size and how tightly it was wrapped, which is why guessing is risky. University of Missouri Extension puts round bale density at 9 to 12 pounds of dry matter per cubic foot, so a 5 x 5 bale holds about 880 to nearly 1,200 pounds of feed. University of Florida cites 700 to 900 pounds as common. Weigh a few of your own bales.
Only as a rough screen. Published alfalfa rules range from about 126 to 225 pounds of dry matter per acre per inch of height, so the same 26-inch stand comes out anywhere from 1.6 to 2.9 tons. Height also misleads in thin stands under 55 stems per square foot. It works for deciding whether to go clip; it is not accurate enough to price a sale.
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