Google truncates on width, not on characters
This is the single most repeated piece of bad advice in on-page SEO. "Keep titles under 60 characters" is an average dressed up as a rule. Google renders desktop titles in Arial at 20px and cuts them at roughly 600 pixels, and characters are not the same width - a title of narrow letters fits far more than one full of capitals and Ms.
This preview measures the thing that actually decides it, using a fixed table of Arial advance widths. That means the answer is deterministic: it is the same on your machine as on ours, which a canvas-based measurement cannot promise because it shifts with whatever fonts happen to be installed.
The budgets
- Desktop title - about 600px, Arial 20px
- Desktop description - about 990px, Arial 14px
- Mobile title - about 490px
- Mobile description - about 680px
Google will probably rewrite it anyway
Title tags get rewritten on a large share of queries, and descriptions are regenerated from page content whenever Google decides something on the page answers the query better. Neither is a reason to skip writing them - a good title is what Google rewrites from - but it is a reason not to agonise over a single character.
Worth pairing with the headline analyzer, which checks the H1 the reader lands on rather than the title they clicked.