The Magic Number: 6 Inches

As a rule of thumb, the minimum end-to-end (length) additional space you'll need for a clawfoot, pedestal, or freestanding tub is 6 inches.  Any less and the tub will look cramped in the space.

For tubs with drains at the end, you'll need a minimum of 4 inches for the floor-mount faucet, with 2 inches padding on the opposite end (as shown).  For wall-mount faucets, you'll reverse this with 2" at faucet, 4" on opposite side,  and  for deck-mount faucets or tubs with center drains, simply center the tub within the 6" space.

The 6/12 Rule

The second rule-of-thumb that we can share is the front-to-back spacing that you'll need.  In this example, we're using a freestanding tub with center-back drain, however the same applies for any stand-alone tub configuration.

The "6" of the 6/12 rule is simply what we explained earlier; you'll want a minimum of 6" of combined additional space on the left and right side of the tub.  The "12" therefore applies to the minimum total negative space you'll want for the front and back of the tub as you work around other objects in your bathroom.

Keep in mind that code requirements typically ask for a minimum of 34" wide and 21" deep access area for the tub (as shown to the left of the vanity).  So the 12" of the 6/12 rule applies only to partial space restirctions.  Within this 12" allotment, it is generally advised to place more room at the front versus the back of the tub.