If you asked most people what the round bales they baled or bought weighed they would probably tell you a number between 1,000 and 1,200 pounds. Why? Because that’s what the guy that sold them the bale or the baler said, right.
It seems strange that producers (rightly so) insist on an accurate weight on cattle bought or sold, feed deliveries, fertilizer loads and other purchases but seem lax about the weight of the bales they buy or sell. When buying or selling bales of hay or baleage, one should know the tonnage or weight of the lot being purchased. Buying by the bale (i.e., $ per bale) can lead to paying an amount that is too high or too low for the value of the hay.
In addition, the only true way to know what a bale or a lot of hay weighs is to actually weigh it. It is rare that anyone will actually know the weight of their bales. At times it may be inconvenient to have a scale of sufficient size to weigh the bales. Also, some sellers may be put off if the buyer insists on weighing the bales prior to purchase.
In those cases Table 1 (below) may be useful. Bale density is a huge variable that can be difficult to estimate. Most modern round balers will make a bale that is between nine and twelve pounds of Dry Matter per cubic foot. If bales are loose and spongy when pressed, it is likely that those bales have a bale density of 9 lbs DM per ft3 or less. If the bale deforms only slightly when pressed or spiked, it is likely to be approximately 10 lbs DM per ft3. If the bale is rigid but deforms when pressed hard or spiked, it is likely to be approximately 11 lbs DM per ft3. If the bale is very rigid and only deforms under the tractor's weight, it is likely to be approximately 12 lbs DM per ft3. Please note that the values listed in Table 1 are merely estimates of bale weight.
Buying hay by weight rather than by the bale is the only fair way, but it may make the transaction harder. In fact, just as with bale weight many folks tend to overestimate bale density. Therefore, one should assume the bale’s weight is approximately 10% less than indicated in the table. Also note that these values are on a dry matter basis. To convert to the actual as fed or wet weight divide the estimated dry matter weight by the percent dry matter of the bale. For example, if the hay is at a stable 12% moisture and the table estimate is 1080 lbs of DM, then the actual “as-fed” or wet weight is 1227 lbs (1080/.88).
Of course, knowing how much hay one is actually purchasing is only the first step to coming up with a fair price. Knowing what hay is selling for and how much nutritive value that a hay lot will provide through a forage test is the key to settling on an equitable price.