Why flat-lays decide your measurement accuracy
Size AI's measurement engine is calibrated for flat garments under even light. The app's accuracy spec, ~5 mm (1⁄5") typical with LiDAR in ideal conditions, assumes the garment is genuinely flat. Wrinkled, slanted, or partially-folded garments break the calibration.
The accuracy gap between an average user and a power user isn't the model. It's the flat-lay.
The good news: getting a perfect flat-lay takes 90 seconds. Most fashion sellers are doing 3-4 things wrong without realizing it. This is the cheat sheet.
12 tricks for perfect flat-lays
1. Use a hard surface
Carpet absorbs the garment's natural drape and fakes a smooth shape. Hardwood, tile, or a lay-flat board gives the camera a clean depth reference.
2. Smooth the fabric outward, not down
Pressing fabric flat with downward strokes creates static folds. Smooth from the center outward in light strokes. The garment relaxes into the surface.
3. Button or zip structured garments
Open jackets and blazers measure differently from how they're worn. Closed garments give you the silhouette buyers actually see.
4. Align the inseam on pants
Even small inseam twists shift length measurements by 1-2 centimeters. Drag your hand down both legs and align the inner seam to the floor.
5. Stand directly above the garment
Crouching at an angle introduces perspective distortion. Stand vertical, hold the iPhone above the garment, look down at it like you're looking at a page on a desk.
6. Follow Precision Guidance
Precision Guidance is on by default. Hold the phone over the garment until the level guide's two circles merge into one green circle, and check that the lights at the top of the screen (distance, steadiness, light) are green before you tap the shutter.
7. Use background contrast
Light garments on a dark surface, dark garments on a light surface. The model leans on contrast. Even slightly mismatched backgrounds shift keypoints by a few pixels.
8. Keep the entire garment in frame
The model interpolates from edges. If the hem extends beyond the frame, the system has to guess where it ends. Step back until the whole garment is visible.
9. Skip mixed lighting
Daylight + overhead bulbs create color casts that confuse the model. Pick one. Daylight is best.
10. Iron heavy fabrics
Cotton, denim, and canvas hold creases. A 60-second pass with an iron eliminates measurement error from wrinkle shadows. Lightweight fabrics (jersey, silk) usually self-smooth.
11. Glance at the arrows
The app draws the measurement arrows on the garment right after capture, placed automatically. A quick glance before you save is all it takes.
12. Move a point in the rare case one is off
If a point ever sits off the edge, the in-app Precision Editor lets you move it, and the measurement recalculates on the device.
What the model is actually looking at
Three things, in order of weight:
- The garment's outline against the background. Contrast > everything else.
- The depth map from LiDAR. Wrinkles and folds show up as depth noise. The model has to disambiguate fabric stack from garment edge.
- The fabric's surface texture. Texture cues help the model identify panels (collar, cuff, pocket, hem).
If a flat-lay nails contrast and minimizes wrinkles, the other two factors matter less. That's why these 12 tricks center on those two variables.
The one habit worth keeping
The post-capture screen shows every measurement arrow on the garment, placed automatically. A two-second glance before you tap "Save to Library" is all the review it needs.
Glance, then save.
For the deeper walkthrough, including specific lighting setups and surface recommendations, see the full Capture Guide. The Precision Guidance feature referenced above ships in the Size AI iPhone app on every supported device.
A clean flat-lay pays off twice. The same capture that lands accurate measurements also feeds a clean product shot, so a well-lit, wrinkle-free layout is what becomes a ghost mannequin listing photo and the kind of images covered in the 15-second ghost mannequin method.
