Complete the proportion:

If is to

then will be to X

Enter the three known values to find X.

This tool helps you quickly solve proportion problems using the rule of three. You fill in three known values, and it calculates the fourth one at the moment. You don’t need to do math in your head or break out a calculator. The tool is fast, private, and there are no sign-up required.

How Rule of Three Works

Simple: you enter three values — for example, if 2 apples cost $4, and you want to know how much 5 apples cost. You fill in the known values, and the tool finds the missing one, X. It’s perfect for quick calculations in everyday situations, whether you’re shopping, working on a project, or just trying to figure out some ratios.

Use Cases

You can use it for all kinds of stuff:

Price comparisons: If a product costs $20 for 5 units, how much for 8 units?
Scaling recipes: If a recipe serves 4 but you need to make enough for 10, what’s the new ingredient amount?
Converting measurements: If 3 miles take 45 minutes, how long for 8 miles?

The interface is simple: fill in the three known values, click “Calculate X”, and bam, you got your answer. No fuss, no download, no account. Just a clean tool made for people who work online and need quick, private calculations.

Privacy and Security

Remember, it’s designed for speed and privacy. All your data stays on your device — nothing gets sent to servers. Use it as much as you want, whenever you need it. That’s how Cliday tools work — fast, free, and secure.

Did you know? Your browser-based proportion calculator is actually more private than most apps because it never sends your data anywhere — it runs entirely on your device, keeping your info safe without any extra effort.

Q&A

Is this tool accurate enough for serious calculations or just rough estimates?

It’s accurate for basic proportion problems, same as any calculator. Don’t rely on it for complex math—this is for quick, everyday stuff, not precision engineering.

If all data stays on my device, how can I trust it’s private?

Because it runs entirely in your browser, your data never leaves your machine. No servers, no logs—your info stays with you, period. That’s real privacy.

Can I use this for anything besides simple math problems?

It’s designed for basic proportion tasks—shopping, recipes, measurements. Don’t try to turn it into a full-blown calculator or math solver. Keep it simple.

Why should I use this instead of just doing the math myself or using a calculator?

Because it saves you time and mental effort—no need to break out a calculator or think through ratios. It’s fast, private, and built for people who work online and need quick answers.

What if I want more advanced features or other tools?

This tool’s just for simple proportions. For anything complex, you’ll need a different calculator or software. We focus on what’s fast, easy, and private—nothing more.