Whether you're about to lay floor tiles, install a kitchen, fit a new appliance, or troubleshoot a wobbly piece of furniture, checking if your floor is level is the first step. An unlevel floor affects everything built on top of it — tiles crack at grout lines, cabinets won't hang flush, and furniture rocks on its legs.
What you need to check a floor for level
Your phone with Spirit Level Online open in the browser, and optionally a long straight board (1–2 metres) to span larger areas.
Understanding what level means for floors
A floor doesn't need to be perfectly flat — it needs to be level. Flat means no bumps or dips. Level means it doesn't slope. Most floor installations tolerate up to 3 mm over a 1.8 m span before it becomes a practical problem. Beyond that, self-levelling compound or shimming is needed before laying anything on top.
Step-by-step: how to check if a floor is level
Start at one end of the room. Place your phone flat on the floor and open Spirit Level Online in Surface Mode. Note the reading — both the left-to-right and front-to-back angles.
Move across the room in a grid pattern. Check several spots — corners, centre, along the walls. Write down or remember the readings at each point. You're looking for consistency, not just one reading.
Use a long board for accuracy over distance. Lay a long straight board on the floor and place your phone on top of it. This averages out small bumps and gives you the true slope over a longer span — much more useful for tiling decisions than a single-point reading.
Identify high and low spots. A reading of 0.0° everywhere means the floor is level. Consistent readings in one direction mean a slope. Varying readings in different spots mean an uneven surface that needs compound before tiling.
Mark any problem areas. Use chalk or masking tape to mark spots where the reading deviates significantly. This helps you know exactly where to apply levelling compound or shimming.
Tip: Acceptable tolerance for common flooring. Ceramic and porcelain tiles: max 3 mm over 1.8 m. Hardwood and laminate: max 5 mm over 1.8 m. Vinyl and LVT: max 3 mm over 1.8 m. If your readings exceed these, self-levelling compound is the right fix before laying the floor.
What to do if the floor isn't level
For small dips and humps (under 10 mm), self-levelling compound poured over the subfloor will find its own level and set flat. For larger slopes — common in older homes where the structure has settled — you may need to build up a subfloor using battens shimmed to level before laying the finish floor on top.
Checking under furniture and appliances
If a piece of furniture wobbles or an appliance rattles, slide your phone underneath on a flat rigid surface to check the floor level at that exact spot. A small floor slope is often the cause of wobbly furniture — adjustable feet on the furniture are the easiest fix, rather than levelling the floor itself.
For all your levelling needs — floors, walls, appliances, and more — Spirit Level Online works directly in your browser with no app download required.