Toilet Not Level: How to Level a Toilet on Uneven Floor

Floor-mounted toilets tolerate a small amount of floor variation, but once one side of the base lifts noticeably off the floor, the seal between the toilet horn and the wax ring begins to flex with every flush. Over months, that flexing breaks the wax ring, which allows wastewater to seep under the floor and allows sewer gas to enter the room. Fixing a toilet that is not level is a repair that repays itself quickly in both plumbing integrity and daily comfort.

Before reaching for tools, it helps to know whether the toilet is truly out of level (the base is not horizontal) or merely rocking (the base touches the floor at two points but not at a third). Both problems feel similar underfoot, but the fix is slightly different. A spirit level laid across the bowl rim tells you within seconds which situation you are dealing with.

What causes a toilet to be not level?

How do you check if a toilet is level?

A quick diagnostic sequence takes less than five minutes and avoids spending money on parts you do not need:

1. Lay a spirit level across the bowl rim side to side and front to back. Note which direction is low.
2. Press on each corner of the base. Any corner that lifts tells you the floor is higher there than you might think, or the base is unsupported at that point.
3. Check the toilet bolts (closet bolts). Grasp the toilet firmly and try to rock it. If it moves with very little force and the bolts are not tightened, loose hardware is the primary problem.
4. Look for water stains or a damp ring around the base. Staining suggests the wax ring has already been damaged by movement, meaning the toilet needs to come up for a new ring regardless of the leveling fix.
5. Check for a soft or springy subfloor. Kneel and press the floor around the base. Softness points to water damage that must be repaired before the toilet can be set properly.

How do you level a toilet with shims?

Step-by-step: Leveling a toilet with shims (no toilet removal required)

This is the correct method when the toilet is out of level but the wax ring appears intact (no water staining, no sewer smell).

Tools and materials needed: spirit level, plastic toilet shims, utility knife, painter's tape, silicone caulk (white or tile-matched), caulk gun, adjustable wrench.

1. Confirm the toilet is not rocking: Tighten both toilet bolts evenly to snug (do not overtighten, which can crack the base). Recheck for rocking. If tightening stops the movement, you may not need shims at all.
2. Identify the low point: Lay the level across the bowl rim. Note which side drops. That is the side you will shim.
3. Slide shims into position: Starting at the low corner, push a shim thin-end-first under the porcelain base. Most floors need one shim per low corner. Push gently until the toilet stops rocking under hand pressure.
4. Recheck with the level: The bubble should now sit centered or very close to it. Add a second shim if you are still more than 1/16 inch off.
5. Score and trim: Once satisfied with the level, mark the shim where it exits the base and score it with a utility knife. Snap off the excess so it does not protrude beyond the toilet footprint.
6. Tighten the bolts: Alternate between the left and right bolt, turning each a quarter turn at a time. You want firm, not tight. Overtightening cracks the porcelain mounting ears. The toilet should not rock. If it does, add more shim before tightening.
7. Apply caulk: Run a bead of silicone caulk around the full perimeter of the base. Smooth it with a wet finger. Leave a small 1-inch gap at the very rear of the base, which allows water from a future wax ring failure to escape where it can be seen rather than pooling unseen under the toilet.
8. Allow to cure: Most silicone caulk reaches a working cure in 24 hours. Avoid heavy use of the toilet during that period if possible.

When do you need to remove the toilet to fix the leveling problem?

Step-by-step: Removing the toilet, fixing the floor or flange, and resetting level

This is the correct approach for cases involving a failed wax ring, damaged flange, or uneven subfloor.

Tools and materials needed: adjustable wrench, hacksaw (if bolts are corroded), putty knife, wax ring, closet bolts, flange repair kit (if needed), spirit level, shims, silicone caulk, bucket and rags.

1. Shut off the water supply: Turn the shut-off valve behind or below the toilet clockwise until it stops. Flush to empty the tank. Sponge out remaining water from the tank and bowl to reduce weight.
2. Disconnect the supply line: Unscrew the flexible supply line from the bottom of the tank by hand. Have a rag ready for residual water.
3. Remove the flange bolt caps and nuts: Pry off the plastic caps at the base. Use an adjustable wrench to remove the nuts. If the bolts spin, grip them with pliers. If they are corroded and will not turn, cut them with a hacksaw just above the nut.
4. Lift the toilet: Grasp the bowl at the front and the tank at the rear. Lift straight up. A standard two-piece toilet weighs 60 to 100 pounds. One-piece toilets from brands like TOTO (the UltraMax II), Kohler (Santa Rosa), or Woodbridge (T-0001) can weigh 90 to 130 pounds. Use help for heavy models.
5. Lay the toilet on its side on cardboard or old towels.
6. Stuff a rag into the open drain flange to block sewer gas while you work.
7. Scrape the old wax: Use a putty knife to remove old wax from the flange and from the toilet horn. Both surfaces need to be clean for the new ring to seal correctly.
8. Inspect and fix the flange: A flange sitting at or slightly above finished floor level is correct. If it is below floor level (common after new tile is installed), use a toilet flange extender kit. If it is cracked or broken, use a stainless flange repair ring that bolts over the existing flange. Do not set a toilet onto a damaged flange and expect it to hold.
9. Check the floor for level: With the toilet removed, lay a spirit level across the flange and across the floor where the toilet will sit. Note any low points. This is the time to address subfloor softness. Press on the subfloor around the drain opening. Soft spots indicate moisture damage; affected areas need to be cut out and replaced with exterior-grade plywood before reinstalling the toilet.
10. Set new closet bolts: Drop new brass closet bolts into the flange slots at the 3 and 9 o'clock positions. Most flanges have two slot positions. Position the bolts so they are parallel and equidistant from the wall behind the toilet.
11. Place the wax ring: Press the new wax ring onto the toilet horn (the flared underside of the toilet bowl) with the wax side facing down. Some plumbers prefer to place the ring on the flange instead. Either method works, but placing it on the horn gives better control during placement for a single installer.
12. Lower the toilet onto the flange: Straddle the bowl or have a helper hold the front while you guide the toilet holes over the closet bolts. Lower straight down. Press firmly with both hands to compress the wax ring. Do not rock or twist the toilet after the wax contacts the flange, which breaks the seal.
13. Level before tightening: Sit on the toilet briefly to compress the wax, then lay the spirit level across the bowl rim. Insert shims under any low corners before hand-tightening the nuts. Get the toilet level and non-rocking before applying wrench torque.
14. Tighten the nuts evenly: Alternate left and right, a quarter turn at a time. Stop when the toilet is snug and does not move. Do not overtighten.
15. Snap on bolt caps, reconnect the supply line, turn water on, fill and flush twice, and check for any leaks at the base and supply line connections.
16. Caulk the base as described in the shimming steps above.

Does an unlevel toilet affect flushing performance?

If you have been dealing with a toilet that seemed to lose flushing power gradually, check whether it has also started to rock slightly. The two problems often develop together. Owners of the best flushing toilets report that a properly sealed, correctly leveled installation restores flush performance to spec without any other adjustment.

Toilet shim types compared

How much can a floor slope before a toilet must be shimmed?

Any slope that causes the toilet to rock is enough to warrant shimming. Structurally, floors are built to a tolerance of 3/16 inch over 10 feet, per standard residential construction practice. Toilet bases are typically 14 to 18 inches wide, which means a floor out of tolerance can create a gap of 1/16 inch or more under one corner of the base. That is sufficient to allow micro-movement during use. The wax ring tolerates very little movement before it separates from either the flange or the toilet horn.

In bathrooms with large-format tile, the tiles themselves are often perfectly flat, but the grout lines between tiles fall fractionally below the tile surface, and a toilet base sitting across multiple grout lines will rock slightly. The fix in that situation is to shim the rocking corner to bridge the grout lines or to remove a very small amount of grout at the high point using a grout saw. Shimming is almost always faster and less risky to the tile.

Can you use caulk alone instead of shims to level a toilet?

No. Caulk is flexible and will compress under the weight of the toilet plus a seated person, meaning the toilet will sink to its lowest position regardless of how much caulk you apply. Caulk around the base is a sealant and cosmetic finish, not a structural support. Shims must carry the load. Caulk then seals around the shims to prevent moisture from getting under the toilet base and causing floor damage over time.

A related question comes up with grout. Some homeowners grout the toilet base to the tile floor. This is not recommended by any major toilet manufacturer, including TOTO, Kohler, American Standard, or Gerber. Grout is rigid and inflexible. A toilet that shifts at all, even microscopically during flushing, will crack grouted joints, which then allows water infiltration that is worse than the problem you were trying to solve.

Related repairs often needed at the same time

A toilet that has been rocking for a significant period may need more than shims and a new wax ring. Check for these related issues while the toilet is accessible:

• Supply line condition: Braided stainless supply lines have a service life of roughly 5 to 10 years. If yours shows any kinking or discoloration, replace it while the toilet is already off. Replacement supply lines are inexpensive and the failure of an old line under pressure causes significant water damage.
• Flapper and fill valve: While the water is off, check whether the flapper is soft and pliable or has hardened. A hardened flapper allows the toilet to run constantly. If you are opening the toilet tank anyway, a fill valve replacement takes 15 minutes and costs very little.
• Toilet bolt condition: Brass closet bolts resist corrosion well, but zinc-plated steel bolts corrode quickly in a wet bathroom environment. If the bolts are visibly rusted or the nuts will not turn cleanly, replace the entire closet bolt set. They are sold in pairs and are inexpensive.
• Base caulk: Old caulk around the base may have mildew or be pulling away. Remove it completely with a utility knife and apply fresh silicone rather than caulking over an existing failed bead.

For a complete guide to this type of work, see our article on toilet leaking at the base and our wax ring replacement guide. If your toilet was already wobbling before you noticed the leveling issue, also review our notes on tightening a loose toilet.