Enrichment · Passion Projects · Video

Wide to tall,
tall to square:
bars or crop, to the pixel.

Type the source size and choose the new shape. The converter gives the output frame and shows exactly how much is cropped or how wide the bars are, before you export.

Convert a frameWhat you get

The aspect ratio converter

The worked example is made up: a 1080p science fair trailer reframed as a vertical reel. Nothing you type leaves this browser.

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What you get

Enrichment · Passion ProjectsFree

What you finish with
The source ratio in lowest terms, the output frame, the scaled picture, the bars or crop on each side and the share kept, with a preview. It prints as a summary and downloads as a spreadsheet.
Who it is for
Students making videos for class, clubs or social media; media teachers; yearbook and school news teams.
Format
Browser calculator for a phone, tablet or computer, by touch or keyboard. Prints a summary; downloads a spreadsheet (.csv); export and import a file.
Access
Free. No account, no sign-in and nothing to install. Everything you type stays in this browser; nothing is sent to Caveat.
Where it lives
The Passion Projects space in Caveat Enrichment.
Support
Questions, a correction or a request: team@caveatacademic.com.

How to use it

  1. Type the source width and height.
  2. Choose the target shape and, if you like, the width.
  3. Choose fit (bars) or fill (crop).
  4. Read the frame size and the crop or bars; check the preview.
  5. Set your editor’s sequence to the frame size shown.

Convert a frame

How the conversion works

A ratio, a frame and one scale factor.

The worked example: wide to verticalSource16:91920 ÷ 1080, by the GCD 120Target frame1080 × 19201080 ÷ (9 ÷ 16)Fill scale177.8%larger of 1080/1920, 1920/1080Crop each side1166.7 px31.6% of the width keptThe worked example: wide to verticalSource16:91920 ÷ 1080, by the GCD 120Target frame1080 × 19201080 ÷ (9 ÷ 16)Fill scale177.8%larger of 1080/1920, 1920/1080Crop each side1166.7 px31.6% of the width kept
Filling a tall frame from a wide picture means scaling up until the height fits, then cutting the sides; fitting means scaling down until the width fits and adding bars.

Ratios

An aspect ratio is width to height. Dividing both by their greatest common divisor gives lowest terms: 1920 × 1080 shares a factor of 120, giving 16:9. The new frame keeps the target width and divides by the target ratio for the height; both are rounded to even numbers because common video codecs store colour in 2 × 2 blocks.

Fit or fill

Fit scales the picture by the smaller of the width and height factors, so all of it shows and bars fill the gap. Fill scales by the larger, so the frame is covered and the overflow is cropped. Going from 16:9 to 9:16 by filling keeps under a third of the width, so frame the subject in the centre when you film.

Sources

  1. International Telecommunication Union. Recommendation ITU-R BT.709: parameter values for HDTV, 16:9 at 1920 × 1080 (itu.int).
  2. Society of Motion Picture and Television Engineers. SMPTE ST 274: 1920 × 1080 image structure (smpte.org).
  3. Poynton, C. (2012). Digital Video and HD: Algorithms and Interfaces (2nd ed.). Morgan Kaufmann: chroma subsampling and picture aspect ratio.
  4. National Council of Teachers of Mathematics. Principles and Standards for School Mathematics: ratios and proportional reasoning (nctm.org).

The worked example is made up. Check each platform’s current upload guidance before publishing. Your figures stay in this browser. Support: team@caveatacademic.com.