Guides · Floor Plan Measurement
Accuracy depends almost entirely on two things: the quality of your input floor plan and how precisely you set the scale. Here's what to expect from each type of source, and how to maximize precision regardless of what you're working with.
CubiCasa PDFs: 1–2%. AI-generated from listing photos but highly accurate. Labeled dimensions let you calibrate precisely. Matterport schematic floor plans: 1–3%. LiDAR-based scanning produces tight accuracy. Use labeled room dimensions for calibration. iGUIDE PLANIX: 1–2%. Laser-measured, among the most accurate residential floor plans available. Note: iGUIDE measures interior (wall-to-wall), not exterior. Architect drawings: 1–2%. Drawn to precise specifications; high-res PDF uploads trace cleanly. Apex Sketch / appraiser sketch exports: 1–3%. Field-measured inputs; exported PNG/PDF reflects underlying accuracy. Phone-photographed prints: 2–5%. Overhead centered shot minimizes distortion. Use longest available scale reference. Hand-drawn sketches with labels: 5–10%. Accuracy depends on how carefully drawn. Non-scale or distorted images: unreliable. Without a scale reference there is no reliable calibration.
Scale reference quality is the dominant factor. A long, precisely known wall segment dramatically outperforms a short, estimated reference. Tracing precision: Clicking exactly on exterior wall corners matters. Zoom in before each point placement. Image resolution: Higher resolution = more precise tracing. PDF originals almost always outperform screenshots. Image distortion: Perspective distortion from angled photos is the biggest single error source. A scanned or digitally-exported plan has zero distortion.
After measuring, trace a room with labeled dimensions: a bedroom labeled "12 × 14" should return approximately 168 sq ft. If it doesn't, recalibrate your scale reference. For multi-floor homes, verify that floor 1 and floor 2 polygon areas are consistent with what you'd expect from the floor plan layout. A 30% discrepancy between floors when the home looks like a simple two-story usually indicates a tracing error on one level.
Many licensed appraisers use this tool to verify GLA and cross-check field sketches. For appraisal use the tool is a verification and calculation aid: the appraiser's field measurement and professional judgment remain authoritative. For buyer and investor research, a 1–3% measurement from a CubiCasa or Matterport plan is more than sufficient for informed decision-making.
Ready to measure your floor plan?
Upload your floor plan and trace square footage in any browser: no software required.
Start Measuring →How accurate are CubiCasa floor plans?
CubiCasa floor plans are generally within 1 to 2 percent of field measurements for the perimeter. Scale calibration in their scanning process is well-controlled. The main accuracy risk is room boundaries in cluttered spaces where the AI may misidentify wall locations.
What about Matterport accuracy?
Matterport schematic floor plans are within 1 to 3 percent of field measurements. Their accuracy depends on capture quality (number of scan points) and how well the AI traces walls in complex layouts. Tighter spaces and curved walls have more variance.
How accurate are hand-drawn floor plans?
Hand sketches vary widely. A professional appraisal sketch (Apex, hand-drawn but to-scale) is typically within 2 to 4 percent. A casual homeowner sketch is often 5 to 10 percent off, depending on how carefully dimensions were measured and recorded.
What about photos of floor plans?
A flat overhead photo with even lighting is within 2 to 4 percent. A photo taken at an angle introduces perspective distortion of 5 to 10 percent. Always photograph floor plans flat from directly overhead.
How can I verify a measurement is accurate?
Set scale from one labeled dimension, then check that a second known dimension on the plan matches what the tool reads after calibration. If the two agree within 1 to 2 percent, the trace and scale are reliable.