Step 1: Measure for the right seat
Three measurements: (1) bowl shape — round-front (smaller, ~16.5 inches lip to bolt holes) or elongated (larger, ~18.5 inches); (2) bolt-hole spread — standard is 5.5 inches center-to-center but verify yours; (3) color — most toilets are "White" (specific shade) but Kohler "Biscuit" and TOTO "Cotton White" are distinct. Take a photo of the original seat label or bring the old seat to the store.
Step 2: Choose the seat type
Plastic standard ($15-30): economy pick, durable, slightly slippery. Bemis 1500EC, Mayfair 18SLOWA.
Wood ($25-50): warmer feel, traditional aesthetic, slightly heavier. Bemis 200E.
Soft-close ($30-60): the lid closes slowly via a hydraulic damper instead of slamming. Default modern pick. Eliminates the toilet-lid-slam wake-up. Kohler Cachet, Bemis 1200SLOWT, Mayfair Slow-Close.
Heated/bidet seat ($150-400): aftermarket smart-seat upgrade. Brondell Swash, TOTO Washlet C100, Bio Bidet BB-2000. Requires GFCI outlet within 4 feet of the toilet.
Quick-release ($30-50): seat pops off the hinges for easy cleaning under the bolt covers. Worth the $5 premium.
Step 3: Remove the old seat
Open the bolt-cap covers at the back of the seat (most flip up with a fingernail or small flathead). Hold the brass or plastic bolt head on top with one hand, unscrew the wing nut underneath with the other. If the bolt spins without unscrewing — extremely common after years of use — use channel-lock pliers to grip the bolt head from above while turning the wing nut.
Step 4: Clean the bolt holes
Mineral and grime accumulate around the seat bolts. Wipe with a disinfecting wipe and a Q-tip. This is the only chance you\'ll have to clean this area without removing the new seat — take 60 seconds.
Step 5: Install the new seat
Most modern seats use plastic or rubber-coated bolts with built-in retainers. Drop the bolts through the hinge holes from above, push down through the bowl holes, secure from below by hand-tightening the wing nuts. Adjust the seat alignment (centered on the bowl, no twist) before fully tightening. Then snug — finger-tight is enough, do not wrench.
Step 6: Test the soft-close action
If you bought a soft-close seat, raise the lid and let it fall. It should descend smoothly over 3-5 seconds. If it slams: the hinge isn\'t engaged properly — pop the seat off and re-seat the hinge cartridges.
Lifespan
A quality soft-close seat lasts 5-8 years. The hydraulic dampers eventually fail (lid begins to fall normally); that\'s the replacement signal. Plastic seats discolor and warp after 7-10 years in heavily-used bathrooms. Wood seats last 10-15 years but the finish degrades sooner.