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Compound Interest Calculator
See how savings grow with compound interest.
Open toolProfit Margin Calculator
Calculate profit margin and markup.
Open toolCoin Flip
Flip a virtual coin.
Open toolLength Converter
Convert metres, feet, inches, and more.
Open toolPercentage Calculator
Find percentages, increases, decreases, and reverse percentages.
Open toolWord Counter
Count words, characters, sentences, and reading time.
Open toolGuides
How the numbers work — methods, examples, and limits.
How to calculate a percentage (and percentage change)
Worked examples for finding a percentage of a number, percentage increase and decrease, and reverse percentages — the same methods used in Utiio’s percentage calculator.
Read guideHow UK VAT works: adding and removing 20%
A plain-English guide to adding VAT to a net price, removing VAT from a gross price, and when reduced or zero rates apply — with the 20% worked examples used in Utiio.
Read guideHow mortgage repayments are calculated
The amortising loan formula behind monthly mortgage payments, what deposit and term change, and what a simple calculator leaves out — fees, tax, and affordability.
Read guideWhat BMI means — and what it does not
How Body Mass Index is calculated, the adult WHO categories, why athletes and some ethnic groups need extra context, and how to use Utiio’s BMI calculator as a screening number only.
Read guideHow compound interest grows savings
What compounding means, why frequency and regular deposits matter, and how to read a projection from Utiio’s compound interest and savings calculators.
Read guideHow to estimate paint for a room
A practical method for wall area, doors and windows, coats, and tin coverage — the same approach as Utiio’s paint calculator, with room for wastage.
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