How to Replace a Toilet Seat and Get the Bolts Right

Check the fit before undoing anything

If you're choosing a seat while the old one is still attached, we'd measure before reaching for the wrench. Bowl shape and length decide which replacement to buy, and checking them now can save you a return trip with the wrong seat.

The procedure below applies to conventional seats with bolts passing through the bowl and nuts underneath. Look at that attachment before starting, then read your replacement's installation instructions and keep them beside you until you're finished. Some seats need a different fitting method, even when their overall shape looks familiar.

Round or elongated

Use a tape measure from the screws at the back of the seat to the front of the bowl. You're checking the bowl's length so you can choose between the two main shapes, round and elongated, before getting into the details of mounting the replacement.

The DIY Playbook describes width differences as unlikely to affect function, although a seat may feel narrower or wider. Use those approximate lengths to identify the shape, then confirm the replacement's fit against its own instructions. That keeps the buying decision tied to the seat you're actually installing.

Unbox the new seat and locate its installation hardware before taking the old one off. Most new seats include their own nuts and bolts, so you generally won't need to save the old fasteners for the installation. Keep the new parts together where you can find them.

Get the tools and work area ready

Have a screwdriver that fits the bolt heads, a wrench or adjustable pliers, and your cleaning supplies ready. Wait to begin until you've gathered the tools needed for your particular seat and can finish switching it over. An optional toilet-seat nut wrench can help you reach awkward nuts underneath the back of the bowl.

Clean the existing seat before handling it, using a commercial cleaner. Pay particular attention to the bolts and narrow crevices where bacteria collect. Scrub the bowl and nearby bathroom floor too, because you'll be working close to both while reaching the underside fasteners.

Wear gloves even after cleaning, and put on protective eyewear for work with screwdrivers, wrenches and stubborn hardware. If you're sensitive to dust, use a mask or respirator. Cleaning the work area and protecting yourself are separate parts of getting ready.

Hold the bolt while loosening the nut

Find the two attachment points at the back of the old seat. The bolts may be plastic or metal, and decorative plastic caps may conceal their heads. With this mounting style, you'll work at both ends of each fastener: the head above the bowl and the nut below.

1. If plastic caps cover the bolt heads, gently lift the caps with a flathead screwdriver. Keep the tool from scratching the toilet's surface as you expose the heads.
2. Locate a nut underneath and hold its bolt head still with the screwdriver. Use your fingers or a wrench to undo the nut, then repeat at the other attachment until both nuts are off.
3. Remove the bolts and lift the old seat away from the toilet. The mounting area beneath the old seat is now exposed.

Holding the head keeps the bolt from turning while you work on its nut. Metal hardware may also be corroded and harder to loosen. If it remains seized, stop the removal and ask a plumber to remove the stuck hardware.

Clean beneath the old fittings

Use cleaner and a scrub brush on the newly exposed areas around the rim and mounting holes. Concentrate on the places that were underneath the bolt caps and plastic covers, where the old fittings made cleaning difficult.

Disinfect the exposed mounting area with an antibacterial spray before installing the new fittings. This is your opportunity to clean the surfaces around the old bolts while the seat and covers are out of the way.

Position the seat before fastening it

Set the replacement on the bowl and look straight down at it. Line up the seat's mounting holes with the bowl's holes and check where the seat rests. Establish that position before fastening it, while you can still move the seat to get the alignment right.

If your seat offers two sets of mounting holes, choose the set that best matches the bowl's holes and the intended seat position. On that arrangement, the front holes move the seat farther back. Use the replacement's instructions to choose the applicable holes for its design.

Insert both supplied bolts through the aligned holes before adding either nut or tightening anything. They should slide through smoothly. If a bolt resists, reposition the seat until it fits without force, which also helps you avoid scratching the toilet.

Tighten by hand before using tools

Put the appropriate screwdriver into the first bolt head and hold it still. With your fingers, thread the nut onto the bolt underneath until it sits securely against the underside of the toilet. Repeat for the second bolt so both nuts are tightened by hand.

Keep checking that the seat stays centered as you tighten. Letting it shift during fastening can leave it crooked or loose. For conventional hardware that needs further tightening after the hand-tight stage, use adjustable pliers cautiously.

Fit the covers and check for movement

Check the newly mounted seat for movement. If it wiggles, the nuts are probably still too loose and may need a careful wrench adjustment. Use restrained pressure during that adjustment because both plastic and metal components can weaken or break when pushed too hard.

If your replacement has plastic bolt covers, line them up with their fittings before pressing them into place. These covers generally pop on without tools or much effort. Getting the alignment right protects the cap fittings from damage.

Open and close the seat a few times to check the hinges and watch for side-to-side movement. The finished seat should operate without that wiggle. Use can loosen a seat later, so check its position and hardware again if movement returns and make the same cautious adjustment.