CSS Unit Sandbox
Preview how common CSS units resolve in a live sample.
Watch CSS units resolve live
px, rem, em, %, vw, vh — each CSS unit resolves against something different, and their real sizes are easy to misjudge. This sandbox applies a value in different units to a live sample so you can see how big each one actually renders in context.
Seeing the units side by side, at your chosen base and viewport, builds intuition that a static conversion table cannot. Experiment with the values, understand how each behaves, and use the one that fits your responsive intent.
Private and instant
Everything runs locally in your browser using standard web APIs — nothing is uploaded, logged, or stored on any server — so the tool works offline, responds instantly, and keeps whatever you paste in on your own device. That makes it safe to use even for confidential, client, or internal data you would never send to an unknown website.
Frequently Asked Questions
What does the css unit sandbox do?
It generates CSS from the options you choose and previews the result directly in your browser.
Can I use the CSS in production?
Yes. Copy the generated CSS as a starting point, then review naming, browser support, and design-system fit before shipping.
Does this upload my design values?
No. The generator runs locally in your browser and does not send your input to a server.
Is this free?
Yes. It is a free browser utility with no account required.
Practical utilities for front-end design and implementation work.