It’s July, which means it’s hay season on my northern Wisconsin farm. As soon as we can catch a three-day window of sunshine without any chance of thunderstorms popping up (they can be unpredictable), we’ll cut and bale as many fields as time will allow.

In the meantime, we’re staying busy preparing equipment and stocking up on supplies, including baling twine.

We certainly don’t want to run out. Without twine, our baler can’t tie off the small square bales we produce, and we wouldn’t get very far in the baling process.

If you’re just getting started baling your own hay, you might wonder how to calculate the amount of baling twine you’ll need for the season. It’s not hard, but it does require a little high school algebra and a couple of key numbers to work with—namely, the number of bales you expect to produce and the size of the bales in question.

Hopefully you have an estimate of how many bales you’ll be producing during any given three-day window. If you’re not sure yet, take a guess for calculating purposes. Then buy some extra twine so you’ll have a reserve stockpile if your harvest exceeds expectations.

**Use this checklist to make sure you’re ready for hay season.**

**Calculating for square bales**

Now it’s time to pull out a calculator and start crunching some numbers.

First—how large are the bales you’re producing? If you’re working with square bales, determine the circumference by adding the width (W) to the height (H) and multiplying the result by two.

Then multiple the circumference by the number of strings wrapped around each bale (S). This will give you length of twine used per bale (TPB).

The formula looks like this:

(W + H) x 2 x S = TPB

If your bales measure 3 feet long by 1 1/2-feet high, and each bale is wrapped with two strings, then every bale will use 18 feet of twine:

(3 + 1.5) x 2 x 2 = 18

If you expect to produce 1,000 bales, you’ll need 18,000 feet (18 x 1,000) of baling twine. A pair of 9,000-foot rolls should do the trick.

**Square bales or round—which is right for you?**

**Calculating for round bales**

A different formula can be employed if you’re producing round bales wrapped with twine.

Multiply the diameter of the bale (D) by 3.14 to determine the circumference, then multiply the circumference by the number of times the twine will be wrapped around the bale (R) to determine the length of twine used per bale (TPB):

D x 3.14 x R = TPB

A round bale with a diameter of 5 feet, wrapped 30 times, will require 471 feet of twine:

5 x 3.14 x 30 = 471

Thus, a 16,000-foot role of twine will be sufficient for just shy of 34 bales (16,000 ÷ 471 = 33.97). If you plan on producing 50 bales, you’ll need 23,550 feet of twine (50 x 471 = 23,550).

When coupled with an accurate projection of the number of bales you’ll be producing, these simple formulas can quickly determine how much twine you’ll need to purchase.

Have fun baling!