Stop guessing and start calculating with precision. The Rule of Three is the gold standard for solving proportional problems in seconds. Whether you are scaling a cooking recipe, calculating travel fuel consumption, or working out a discount percentage, our tool does the heavy lifting for you.
Simply enter the three known values, and our algorithm will find the fourth unknown (X) instantly. It is the “Swiss Army Knife” of daily math, designed to be fast, accurate, and incredibly easy to use on any device.
It works on the principle of direct proportion.
If value A is related to value B, then value C must be related to X in the exact same ratio.
Mathematically, the formula is X = (B × C) / A.
Our calculator automates this process instantly, saving you from doing mental multiplication and division, ensuring you never make a calculation error.
Yes, absolutely.
This is one of the best uses for the tool.
For example, if you know that $50 (A) represents 100% (B) of a price, and you want to know what percentage $10 (C) represents, simply input those values.
The result (X) will be the exact percentage. It’s perfect for calculating discounts, tax rates, or project completion stats.
The applications are endless.
Chefs use it to scale recipes (e.g., converting ingredients for 4 people to feed 10).
Travelers use it to convert currencies or estimate arrival times based on speed.
Freelancers use it to prorate their hourly fees for partial work.
Essentially, anytime you need to say “If this is that, then how much is this?”, you need this tool.
Yes, it is specialized for workflow.
A standard calculator requires you to remember the formula and the order of operations.
Here, the visual layout (A → B, C → X) guides your logic naturally.
You don’t need to think about how to calculate; you just need to fill in the blanks.
Plus, our “Copy Result” button streamlines your work when moving data to other apps.
1. Visual Logic Flow:
We designed the interface to mimic the way your brain actually thinks about problems. The “A points to B” layout makes it intuitive to understand the relationship between the numbers, preventing the common mistake of inputting values in the wrong order.
2. High-Precision Accuracy:
Forget about rounding errors or rough estimates. Our algorithm handles decimal points with extreme precision, making it safe for financial calculations, precise engineering conversions, or academic work where every fraction counts.
3. One-Click Copy & Swap:
Productivity is about speed. With dedicated buttons to “Copy Result” and “Swap Values”, you can rearrange your calculation or export the answer to an Excel sheet or email without ever touching your keyboard’s shortcut keys.
💡 Pro Tip: Need to convert units? Set A = 1 and B = conversion rate (e.g., 1 inch = 2.54 cm). Then, type any value in C (inches), and X will instantly show you the result in centimeters!