What you need before you start

A toilet seat replacement takes about 15 minutes and requires only two tools: an adjustable wrench or a socket wrench, and a screwdriver (usually Phillips head, sometimes flathead). You do not need a plumber. The bolts holding the old seat are almost always accessible from underneath the bowl, and the new seat comes with its own bolts and hardware.

Before you buy a replacement, measure your toilet bowl. Most seats are standard oval, but some older toilets are round. Check the distance from the center of one bolt hole to the center of the other — this is usually 5.5 inches on standard toilets. Take a photo of your current seat or bring the measurements to the store. Replacement seats cost between $25 and $150 depending on material and features (basic plastic, soft-close hinges, heated seats, bidet attachments).

Key Takeaways

  • Measure the distance between your toilet's bolt holes before buying a replacement seat, since most are standard oval but some older toilets are round.
  • The bolts are underneath the bowl, accessed by lifting the seat and lid — you do not need to remove the toilet itself.
  • Use an adjustable wrench to hold the nut underneath while you unscrew the bolt from above, so the nut does not spin and strip.
  • New seats come with bolts and washers; tighten them by hand first, then snug with a wrench — overtightening cracks the porcelain.
  • If bolts are stuck or corroded, spray them with penetrating oil and wait 10 to 15 minutes before trying again.

Removing the old seat

Lift the toilet seat and lid all the way up. Look underneath the bowl where the seat hinges attach. You will see two bolts coming up through the bowl, one on each side, with nuts underneath. These bolts hold the entire seat assembly to the toilet.

Place your adjustable wrench on the nut underneath the bowl and hold it steady. This prevents the nut from spinning while you unscrew the bolt from above. Use your screwdriver to turn the bolt counterclockwise. Turn slowly — if the nut spins instead of the bolt loosening, you have not gripped it firmly enough with the wrench. Once both bolts are loose, lift the old seat away from the toilet.

If the bolts will not budge, spray them with penetrating oil (like WD-40) and wait 10 to 15 minutes. The oil soaks into the corrosion and makes them turn more easily. Wipe away excess oil with a rag before you grip the nut again.

Installing the new seat

New seats come with two bolts, two washers, and two nuts. Insert the bolts down through the holes in the new seat, then line the seat up over the bolt holes in the toilet bowl. The bolts should poke straight up through the bowl. Slide a washer onto each bolt, then thread a nut onto each bolt by hand.

Tighten the bolts gradually, alternating between left and right so the seat stays level. Use your wrench to hold the nut underneath while you turn the bolt from above, just as you did when removing the old seat. Tighten until the seat is snug and does not rock side to side, but do not over-tighten — porcelain cracks easily, and you only need the seat to be secure, not locked down.

Test the seat by sitting on it and shifting your weight. It should not move. If it rocks slightly, tighten the bolts another quarter turn. Close the lid and check that it closes smoothly without hitting the tank.

Troubleshooting stuck or broken bolts

If a bolt snaps while you are removing it, the nut will still be attached underneath. You can remove the nut with your wrench, then use pliers to pull out the broken bolt piece. If the bolt is truly stuck and will not turn even after penetrating oil, you may need to drill it out — this requires a power drill and a bit slightly smaller than the bolt diameter. Drill slowly and carefully to avoid damaging the porcelain.

If the bolt holes in the toilet are stripped (the bolt spins but does not tighten), you can buy an oversized bolt kit at a hardware store. These kits include larger bolts and washers that sit on top of the bowl instead of going through it. Installation is the same, but the larger washers distribute pressure over a wider area and prevent cracking.

Soft-close and heated seat installation

Soft-close seats and heated seats install the same way as standard seats — the bolts and washers are identical. The difference is in the hinges and the internal mechanisms. Soft-close seats have a hydraulic damper in each hinge that slows the lid as it closes. Heated seats have an electrical cord that plugs into an outlet near the toilet.

For heated seats, plan where the cord will run before you install the seat. Most cords are about 3 feet long, so the outlet needs to be within reach. Do not run the cord under the toilet or through water — route it along the wall or behind the tank. Plug it in only after the seat is fully installed and secure. Turn on the heating function and let it run for a few minutes to make sure it works before you consider the job done.

When to call a plumber

You do not need a plumber for a standard seat replacement. However, call one if the bolt holes are cracked or if water is leaking from underneath the bowl where the bolts go through. A crack means the porcelain is damaged and the seat will never sit securely. A leak means the wax ring or bolts have compromised the seal between the toilet and the floor, and that requires professional repair.

If you are uncomfortable working underneath the toilet or if you have mobility issues that make bending difficult, a plumber can do this job in 20 minutes for a service call fee (usually $75 to $150 depending on your area). It is a straightforward task, but it is worth paying for if you cannot do it yourself safely.

Frequently Asked Questions

Do I need to turn off the water to change a toilet seat?

No. The water supply does not need to be shut off because you are only removing and replacing the seat, not touching the tank or the bowl's internal mechanisms. The seat bolts are completely separate from the plumbing.

What if my new seat is slightly different in size?

If the bolt holes do not line up with the toilet's holes, the seat is the wrong size for your toilet. Do not force it — return it and buy the correct size. Forcing a misaligned seat can crack the porcelain or strip the bolt holes.

Can I reuse the old bolts and nuts?

You can, but new seats come with new hardware for a reason. Old bolts may be corroded or slightly bent, and new bolts ensure a secure fit. The cost difference is minimal — just use the new bolts that came with the seat.

How tight should the bolts be?

Tight enough that the seat does not rock when you sit on it, but not so tight that you are straining with the wrench. A quarter turn past snug is usually right. Porcelain is brittle and cracks under excessive pressure, so hand-tight plus a small wrench adjustment is the target.