How much screen does a video actually use?
The shape of the screen matters alongside its diagonal. A video fitted without cropping leaves unused space when its shape differs from the display. Change the ratio below to compare a widescreen video, a 4:3 image, a cinema frame or a vertical clip.
The default is 16:9 video with every screen in landscape. “Video diagonal” describes the fitted image, not the complete display. All four diagrams use the same scale within this comparison.
Video image Unused screen · same scale in every panel
| Display | Video area | Video diagonal | Screen filled |
|---|---|---|---|
| Duo · inner | 21.62 in² | 7.11 in | 80.0% |
| Duo · outer | 10.98 in² | 5.07 in | 81.8% |
| iPhone 18 Pro Max | 14.62 in² | 5.85 in | 81.8% |
| iPad mini (A17 Pro) | 27.08 in² | 7.96 in | 85.7% |
Rectangular estimates, not measurements of a running app. Rounded corners, cutouts and player controls are excluded. Diagrams are proportional, not life-size.
Why are there black bars?
Fit-to-screen preserves the complete frame. If the screen is proportionally taller than the video, unused space remains above and below it. If the screen is wider, unused space remains to the sides. Rotating the screen changes which dimension constrains the picture.
Zoom-to-fill is a different choice: it removes unused space by cropping the image. That may cut off subtitles, faces or interface elements near the edges. This comparison intentionally keeps the complete frame, so a high screen-fill percentage is not achieved by hiding part of the video.
An app can also reserve room for playback controls, comments or another window. Embedded bars already present in a video file remain part of that file. Neither is included in these idealized diagrams.
Inputs and calculation
| Display | Rectangular diagonal | Pixel dimensions used for shape |
|---|---|---|
| iPhone Duo inner | 7.58 in | 2670 × 1878 |
| iPhone Duo outer | 5.36 in | 2034 × 1398 |
| iPhone 18 Pro Max | 6.86 in | 2868 × 1320 |
| iPad mini (A17 Pro) | 8.3 in | 2266 × 1488 |
Inputs come from Apple’s Duo specifications, 18 Pro / Pro Max specifications and iPad mini specifications, checked September 16, 2026. We use the stated rectangular diagonals rather than rounded marketing sizes. Real viewable area is smaller because of corners and cutouts.
For a rectangular diagonal D and pixel dimensions P and Q, the side lengths are D × P / √(P² + Q²) and D × Q / √(P² + Q²). With screen width W, height H and video ratio R, the fitted image width is the smaller of W and H × R; its height is image width / R. Multiplying those gives the picture area. Dividing by W × H gives the filled-screen percentage.
This is our geometric calculation, assuming square pixels. It does not measure brightness, image quality, app compatibility or the physical crease. Small differences should not be treated as precise real-world advantages.
Folded and unfolded body dimensions
Apple lists Duo at 117.8 × 84.1 × 11.3mm closed and 117.8 × 164.6 × 5.2mm open, with a weight of 254g. These are body dimensions, separate from the display rectangles above; a case adds its own bulk.
For a rough desk comparison, draw those two height-by-width rectangles on paper with a ruler. That can help visualize the footprint, but it will not reproduce thickness, weight distribution, hinge behavior or grip comfort. The browser diagram is not calibrated to life size.
Use the comparison for your own tasks
Try the aspect ratio you actually watch, then compare the image area rather than ranking devices by screen-fill percentage alone. A small screen can fill a larger percentage while still showing a smaller picture. For reading or documents, video calculations are only a starting point: font size, layout and software behavior also matter.
Explore folding poses in the interactive experience. To place your own media on the virtual phone, follow the animation tutorial. For the rest of the hardware, return to specifications and the buying guide. None of these simulations replaces a hands-on fit check.