Saddle height affects how your leg reaches the pedal and how freely you can turn it. Cycling UK suggests starting with the heel method: sit on the bike, lean against a wall or ask someone to hold it, and put your heel on the pedal at the bottom of its stroke. Your leg should be straight in this position without having to stretch to reach the pedal.
Then place the ball of your foot on the pedal as you would when riding. Your knee should retain a slight bend at the bottom of the stroke. If you have to reach, the saddle may be too high; if the knee remains deeply bent, it may be too low. Make small adjustments and secure the seatpost clamp after each one.
A short ride is the final check: your hips should not rock from side to side as you pedal, and the motion should feel comfortable. The heel method gives you a starting point, not one perfect height for everyone. If discomfort persists, consider the wider riding position instead of repeatedly changing saddle height alone.