Free online tools that just work

No sign-up. What you type never leaves your browser. Pick a tool:

Find the best bedtime or wake-up time based on 90-minute sleep cycles.

Stay focused with 25-minute work sessions and timed breaks.

Convert length, weight and temperature instantly.

Check your Body Mass Index and healthy weight range.

Estimate monthly payments, total interest and payoff time.

Turn any text or URL into a scannable QR code.

Create strong, random passwords in one click.

Format, minify and validate JSON instantly.

Count words, characters and reading time as you type.

Get your exact age in years, months and days.

Why Liwei Tools?

Every tool on this site runs 100% in your browser — nothing you type is sent to any server. Pages are tiny and load instantly, even on slow phones.

Are these tools really free?

Yes. Every tool is free to use with no limits, no accounts and no paywalls. The site is supported by unobtrusive ads.

Do I need to create an account?

No. All tools work instantly — open the page and use it.

Is my data private?

Yes. All calculations happen locally in your browser. We never see, store or transmit what you enter.