How to analyse font metrics: upm, ascender, x-height, cap-height
- Step 1Drop your font — TTF, OTF, WOFF, or WOFF2. The analyser parses the metrics tables.
- Step 2Read the metrics — Output: units-per-em (typically 1000 or 2048), ascender, descender, line-gap (typo and win variants), x-height, cap-height. Three line-height candidates: typo-based, win-based, and a safe maximum.
- Step 3Apply the recommended line-height — Copy the suggested line-height value. Apply via body { line-height: 1.485; } or as a CSS custom property in your design system.
Frequently asked questions
Why three line-heights?+
OpenType has three sets of vertical metrics (hhea, OS/2 typo, OS/2 win). Browsers prefer typo when USE_TYPO_METRICS is set, otherwise win. The analyser shows all three; the 'safe' value is the max — guaranteed not to clip in any renderer.
What's typical UPM?+
TrueType: 2048 (sometimes 1024). PostScript/CFF: traditionally 1000. Modern Google Fonts: standardised on 1000. UPM doesn't affect rendering; it's the internal coordinate scale.
Does x-height matter for design?+
Yes — fonts with similar x-heights can substitute for each other without breaking layout. The Metrics Analyser surfaces this so you can match fallback fonts to web fonts visually.
Privacy first
Every JAD Font tool runs entirely in your browser using opentype.js and the wawoff2 WASM Brotli encoder. Your fonts never leave your device — verified by zero outbound network requests during processing.