Percentage, Fraction & Ratio Calculators
Six calculators for the arithmetic that actually comes up day to day — parts of a whole, and how to move between the ways of writing them.
Percentages, fractions and ratios are one idea in three notations
A half, 50% and 1:1 are the same relationship written three ways, and most confusion comes from switching notation mid-problem. The Percentage Calculator handles the three questions percentages actually answer — what is X% of Y, X is what percent of Y, and the percentage change between two numbers. The Fraction Calculator adds, subtracts and simplifies without decimal rounding, which matters in recipes and measurements. The Ratio Calculator scales a ratio up or down while keeping the proportion, the form mixing and dilution problems come in.
Which average did you mean?
"Average" is three different statistics. The mean is the total divided by the count, the median is the middle value once sorted, and the mode is the most common one. On skewed data they can be far apart — one very high salary drags a mean upward while leaving the median where it was, which is why income is usually reported as a median. The Average Calculator gives all three at once, and reading them together tells you whether the mean is safe to quote.
Percentage change is not symmetric
This is the trap worth internalising: a 20% fall followed by a 20% rise does not get you back. £100 down 20% is £80, and £80 up 20% is £96. The multipliers are 0.8 and 1.2, and they do not cancel. The same asymmetry is why a 50% markup is only a 33% margin — percentages made simple works through it, and the Markup Calculator handles the pricing case.
The two odd ones out
The Basic Calculator is exactly what it sounds like — a keyboard-friendly four-function calculator for when you do not want a tool with a formula behind it. The Roman Numerals goes both ways between Arabic and Roman numerals, which is a genuine need for dates on buildings, book front matter, film credits and monarch numbering. For anything with an unknown in it, move up to the algebra and advanced tools linked above.