ResCal exists for the moment before the export dialog: what dimensions should this become? A 1920×1080 frame going into a square feed, a 4K master that needs a full encoding ladder, a photo that has to fill a 1500×500 header without a crop through someone’s face — each is a small geometry problem, and this page solves it in the open.

Geometry, not image files

Deliberately, the scaler does not touch your images. It computes the numbers — scaled dimensions, scale factors, bar sizes, ladder rungs — and your editor, FFmpeg command or CMS does the actual resampling. That split is the product: it keeps the tool instant, keeps every calculation inspectable, and means there is literally nothing to upload.

Why the numbers are honest

Three conventions on this page exist because the real world demands them:

• The ladder rounds to even. Video codecs (H.264, H.265, AV1) reject odd dimensions outright, so a computed rung like 853×480 would be an export error, not a size. The computed side always rounds to the nearest even pixel.
• Upscales are labeled. Any result that enlarges the source gets flagged — enlarging invents pixels, and pretending a 640×480 can become a clean 1080p is how muddy uploads happen.
• Specs carry a date. The social-media presets were verified in October 2026 and say so on the page; platforms revise these, and an undated spec is a spec you can’t trust.

One page, five modes, zero plumbing

The whole site is static files — HTML, one stylesheet, one script — served through Cloudflare’s edge. There is no account system, no server-side calculator, no database of past queries. Close the tab and nothing about your session persists anywhere.

Neighbors, not duplicates

ResCal lives on nxtolerance.com alongside PixelCalc, which answers the adjacent question — pixel density (PPI/DPI, print sizes). ResCal deliberately never does density math; it stays in pure pixel geometry. If your question involves inches or printers, PixelCalc is the right tool.

Getting it wrong, and fixing it

If a preset disagrees with a platform’s current spec, a ladder rung computes wrong, or a guide has a stale number, that’s exactly what we want to hear — the contact page explains what to send.