What is a Ballast Ratio (keel %)?

The Ballast Ratio is the amount of ballast a design is carrying. This ratio is often displayed as a percentage. The higher the percentage, the greater the righting moment, i.e. better ability to resist heeling. The calculation is very popular because its simplicity and the fact that the values of ballast and the displacement are easily available. The article relates the Ballast Ratio to thousands of sailboats.

How to calculate the Ballast Ratio (keel %)?
Ballast / Displacement ratio
Ballast ratio

BallastkgThe weight of the keel

The unit can actually be kg, ton, lbs, or any other weight unit as long as it is the same for both ballast and displacement.

Ballast ratio scattering
Ballast ratio scattering
This figure shows the scattering of the Ballast ratio for thousands of sailboat designs. Each dot represent a specific design. The figure shows that the most designs has a ballast ratio in the range 30 - 50 %.

Ballast ratio for the average boats
Ballast ratio per length
This figure shows the mean value of the Ballast Ratio as function of the length of the hull. The vertical lines shows the uncertainty in the statistics. If the sample is low - which they are for sailboats < 6 meters (15 feet) and sailboats > 15 meters (45 feet) - then the uncertainty is high, i.e. long lines. The largest keel % is for 10 meter (33 ft) boats, which is 41 % in average.