Aspect Ratio Calculator — Free Cinematic Letterbox & Overlay Generator (16:9, 4:3, 2.39:1)Aspect RatioCalculatorCalculator

2.35:1 was the original CinemaScope anamorphic ratio introduced in 1953. In 1970, SMPTE standardized it to 2.39:1 (often rounded to 2.40:1) to avoid splices in the optical track area. Today, both terms are often used interchangeably, but 2.39:1 is the modern standard for theatrical releases.

Letterboxing adds horizontal black bars (top and bottom) when displaying widescreen content on a narrower display - for example, showing a 2.39:1 film on a 16:9 TV. Pillarboxing adds vertical bars (left and right sides) when showing narrower content on a wider display - like 4:3 content on a 16:9 screen.

Netflix recommends 2:1 (also called Univisium or 18:9) for original content. This ratio is a compromise between cinematic 2.39:1 and television 16:9, working well on both traditional TVs and mobile devices without excessive letterboxing.

For Instagram feed posts, 4:5 (1080x1350px) provides the most screen real estate in the feed. For Stories and Reels, use 9:16 (1080x1920px). Square 1:1 (1080x1080px) works universally but takes up less space in feeds.

Download the PNG or MOV mask from the Film Overlay tab, then import it into your timeline on a layer above your footage. For PNG, set the blend mode to 'Normal'. For MOV with alpha, the transparent center will automatically show your video. In Premiere Pro, DaVinci Resolve, and Final Cut Pro, you can also use the mask as a track matte for more control.

Gate weave is the subtle horizontal and vertical movement that occurs when film passes through a projector gate. It's a hallmark of authentic 16mm and 35mm film projection. Adding gate weave to your letterbox overlay creates an organic, cinematic feel that static digital footage lacks. Our Film Overlay tab lets you adjust both intensity and speed of this effect.

In the Film Overlay tab, click 'MOV (Alpha)' to export a ProRes 4444 video file with a transparent alpha channel. This allows you to layer the animated overlay (including gate weave, vignette, and film grain) directly over your footage in any professional editing software. The MOV format is compatible with Premiere Pro, DaVinci Resolve, Final Cut Pro, and After Effects.

Film grain simulates the random texture of photochemical film stock and affects the entire image. Dirty letterbox effects (dust, scratches, light burns) appear only in the letterbox bar areas, simulating the wear and artifacts found on aged film prints. Combining both creates an authentic vintage film aesthetic.

Yes! The Film Overlay tab supports 1-4 simultaneous cutouts with independent aspect ratios. Choose from layouts like side-by-side, stacked, or 2x2 grid. Each cutout can have its own aspect ratio and scale setting, perfect for comparison videos, multi-cam edits, or creative splitscreen compositions.

For 4K UHD footage (3840x2160), export your letterbox overlay at the same resolution to ensure pixel-perfect alignment. Our tool supports all common resolutions including 4K DCI (4096x2160), 4K UHD, 2K, 1080p, and vertical formats for social media.