Physics of a Grandfather Clock

I used to wonder why the pendulum in a grandfather clock was there, and I originally thought it was for purely visual interest.

Now, I realize that the pendulum acts as a pendulum to keep the clock working at exactly the right time. The pendulum has a period of 1 second and each time it swings left or right, it moves the clock through one second.

But what length should the pendulum be in order to keep time at 1 second?

The equation for the period of a pendulum is T = (2* pi) (L/g)^(1/2) and when plugging in the value of 1 s for T and 9.81 m/s for g, you get that the length of a pendulum to keep time correctly is about .25 meters.