Put in the simplest terms, the ratio of any given spinning wheel is the number of times the flyer turns while the drive wheel makes one complete revolution. Because the flyer inserts the twist into the fibers being drafted at the rate of one twist per revolution, knowing the ratio of the wheel becomes an important factor in determining how much twist will be inserted into the fibers being drafted.

All spinning wheels have at least one ratio. Many have more than one, with 2 or 3 ratios being the most common.

Bobbin and flyer wheels work like this:
For every complete treadling (up, down, back up) the drive wheel makes one complete revolution. For every complete revolution of the drive wheel, the flyer will turn X number of times. The number of times the flyer turns for each complete drive wheel revolution is the ratio. This is written as 1:X with the 1 being the one revolution of the drive wheel and the X being the number of times the flyer revolves.

A ratio of 1:6 means that the flyer makes 6 complete revolutions every time the drive wheel makes one complete turn...which also means that the flyer turns 6 times for each complete treadling action.

A ratio of 1:10.5 would mean that the flyer turned 10 ½ times for each single turn of the drive wheel or each treadling.

The ratio is determined by the diameter of the drive wheel in relationship to the size of the whorl(s) on the bobbin, the flyer, or both. On a bobbin lead wheel (i.e. Louet S-10) the bobbin whorl diameter determines ratio. On a flyer lead wheel with Scotch tension (i.e. Jensen wheels), the flyer whorl diameter determines ratio. On double drive wheels, both the bobbin and flyer whorl determine the ratio.

You can easily figure your ratio(s) quite closely by marking one flyer arm, on drive wheel spoke and turning the wheel so both marks are at the 12:00 o'clock position. Then turn the drive wheel while counting the number of times the flyer turns while you give the drive wheel one turn. This method is quite accurate for single drive bobbin or flyer lead wheels but is not as accurate for double drive or accelerating wheels. For really accurate ratio calculations, a bit of math is needed. For those who want to do the math, the information on how to calculate ratios is here:

(Spinning Wheel Ratios - The Single Drive Systems)
(Wheel Ratios - Double Drive & Accelerating)


The ratio of the wheel tells you how much twist the wheel is inserting into the fibers you are drafting.

It works like this:
Let's assume that your wheel has a ratio of 1:10.
Each time you treadle, the drive wheel turns once and the flyer turns 10 times. Every time the flyer makes one complete revolution it inserts one twist into the fibers that are being drafted. So, when the flyer turns 10 times, 10 twists are into the yarn you are making. If your wheel has a ratio of 1:15, then 15 twists would be inserted per treadling. A ratio of 1:6 would insert 6 twists. So the ratio tells you how much twist the wheel will insert into the fibers.

Knowing how much twist the wheel is inserting is the key to controlling the number of twists per inch (tpi) in your spun yarn.

All that is left is controlling the length of your draft.

It works like this:
Assuming a ratio of 1:10, each treadling adds 10 twists. If you want 10 tpi in your spun yarn, then you must draft one inch of fibers for each treadling. If you want 5 tpi in your spun yarn, then you must draft 2" of fibers per treadling. If you want 20 tpi in your spun yarn then you must draft only ½" of fibers per treadling OR treadle twice for each inch of fibers drafted. Alternatively, if your wheel also had a whorl that would give a 1:5 ration and you wanted to draft one inch of fibers per treadling, you could change to the 1:5 whorl. Or if you had a 1:20 whorl and wanted 20 tpi per treading, then simply switch to that whorl.

A lap cloth with a grid marked in inch or two inch segments helps when it comes to controlling the length of the draft. Start spinning and watch the length of your draft against the markings on the lap cloth. It won’t take long before your hands automatically draft the correct length for each treadling.