How Accurate Is MeasureFloorPlan?
Accuracy in MeasureFloorPlan comes down to two things: the accuracy of your floor plan and the accuracy of your scale setting. Both matter. Here is how to think about it.
The two sources of accuracy (or error)
MeasureFloorPlan is a measurement tool, not a data source. It measures what is in the image you give it. That means accuracy has two variables:
- Floor plan accuracy: Is the floor plan drawn correctly to scale? A professional floor plan from CubiCasa, Matterport, or iGUIDE is already accurate. A hand-drawn sketch or rough diagram will reflect whatever errors the drafter introduced.
- Scale accuracy: Did you click the right points when setting scale, and do you have the exact real-world measurement? A 1% error in scale equals roughly a 1% error in the final area.
What you can expect from a to-scale floor plan
If you are using a floor plan from CubiCasa, Matterport, iGUIDE, or similar professional scan software, the floor plan is already drawn to accurate real-world dimensions. When you set the scale correctly in MeasureFloorPlan, you should land within 1 to 2% of what a field measurement would show.
That level of accuracy is tight enough for most appraisal, listing, and buyer due diligence purposes.
What you can expect from a hand-drawn or rough floor plan
A floor plan that was hand-sketched or drawn from memory may have rooms at the wrong proportions or walls that are not drawn at true scale. MeasureFloorPlan will accurately measure the perimeter as drawn, but if the drawing is not to scale, the calculated area will not match the actual square footage.
For these cases, MeasureFloorPlan is still useful, but treat the result as an estimate rather than a precise measurement.
The scale step is the biggest variable
Most inaccuracy in MeasureFloorPlan results come from the scale step, not from the perimeter detection. Specifically:
- Using an estimated wall length instead of a measured one
- Clicking near the ends of a wall but not exactly at the edges
- Using a short wall (small errors have larger proportional impact)
- Using a diagonal wall (harder to click precisely)
Best practice: pick the longest straight exterior wall you know the exact measurement of. Click precisely at the outer edges of each end. Enter the measurement in feet.
Compared to other methods
Field measurements with a laser measure are the gold standard. MeasureFloorPlan working from a to-scale floor plan gets close, usually within 1 to 2%. County assessor data and MLS square footage often have much larger errors because they are based on permit records, self-reported data, or outdated appraisals.
Learn more: What Is a To-Scale Floor Plan? · How common are MLS square footage errors? · How to calculate square footage from a floor plan