Getting the Scale Right: A Practical Guide

What happens once the scale is set

When you place a sofa that's 180 cm (71 in) wide, it's drawn on screen as a rectangle whose length equals "180 cm ÷ pixels-per-centimeter." In other words, if your scale is off by a factor of two, the apparent size of every piece of furniture will be off by roughly the same factor. The flip side is that once the scale is reliable, comparing catalog dimensions against your room becomes perfectly usable.

The recommended approach (step by step)

Pick one line segment on the plan whose real-world length is explicitly stated (for example, a kitchen width of 2500 mm / 250 cm, a living room width, or a hallway's clear width).
Measure how many pixels that segment spans on screen (be careful not to change your device's zoom level while doing this).
Divide "pixel count ÷ centimeter count" to get pixels per centimeter, then enter that value into the tool.

If you test several dimensions and get wildly different results, some part of the floor plan probably doesn't match its stated scale — this can happen with decorative sketch lines, perspective renderings, or a screenshot that's been altered. When that happens, prioritize the dimension closest to the primary source, such as figures from the real-estate company or the architectural drawing.

Choosing a reference line that won't lead you astray

Use a long wall: measurement error has proportionally less impact on the result (dividing by a short dimension makes a difference of just a few pixels much more significant).
Use a line that's close to horizontal or vertical: lines that run diagonally or curve are hard to distinguish from image distortion.
Stay within a single image: scale won't match between two separate images that have been resized differently, so always measure within one consistent exported image.

Why phones and computers can look different

Even with the exact same saved file, the effective "pixels per centimeter" value can shift depending on your screen resolution, browser zoom, or OS display scaling. If you keep working on a plan over time, it's worth re-checking the scale on whichever device you use most, or re-measuring the reference line on the plan from scratch.

Summary

The scale is the bridge between your floor plan and your screen. Before you share a layout idea with family or a contractor, it's worth double-checking that your reference dimension is sound — it saves you from having to redo work later. See Preparing a Floor Plan Image for more on preparing the image itself.

If the numbers just won't line up

If you try several reference dimensions — a wall length, a room width, a hallway width — and they still don't agree, the image itself may have a mix of problems: perspective, editing, or margin compression. In that case, it's often faster to pick the single most trustworthy dimension as your anchor while also trying a different source image for comparison.

To try it with your own floor plan, open the web app. If you don't have a floor plan on hand yet, you can start with our sample data.