What is X% of Y?
X is what % of Y?
X is P% — what's the original?
This site is the general %-and-tax calculator hub of a four-site family. VAT specialist calculators live on vatcalculator.uk; pension calculators on agecalculator.co.uk; UK grade calculators on maths-help.co.uk.
Popular calculators
Most-used calculators on this site — tap to open.
Take-home pay calculatorCombined PAYE + NI for any UK salary.Salary increase (with tax)Real take-home effect of a pay rise.Stamp Duty calculatorEngland/NI with FTB relief.LTV / mortgagePlace yourself in the right rate band.X% of YThe classic percentage calculation.Compound interestFV with optional monthly compounding.
Guides & examples
Quick paths to the answer you need.
Formulas & glossary
Plain-English definitions of the terms used across the calculators.
PercentageA proportion expressed per 100.
20% means 20 out of every 100, or 0.20 as a decimal.Percentage pointThe arithmetic difference between two percentages. A rate moving from 4% to 5% rose by 1 percentage point (a 25% relative increase).
Base valueThe starting number a percentage is taken from. In "20% of 150", the base is
150.Percentage change
((new − original) ÷ original) × 100. A pay rise from £35,000 to £36,750 is a 5% change.Reverse percentageSolving for the original when given the part and its percentage. £200 = 20% of £1,000.
Compound interestInterest applied to both the original and previously-earned interest.
FV = PV × (1 + r)n.Personal allowanceThe UK 2026/27 income tax personal allowance is £12,570 — earnings up to this are tax-free.
Basic-rate thresholdEarnings between £12,571 and £50,270 fall in the 20% basic rate band for 2026/27.
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Frequently asked questions
How do I work out a percentage of a number?
Divide the percentage by 100, then multiply by the number. 20% of 150: 20 ÷ 100 = 0.20; 0.20 × 150 = 30. 5% of 35,000: 0.05 × 35,000 = 1,750. The X% of Y calculator above does this instantly.
How do I calculate a percentage increase?
Subtract the original from the new value, divide by the original, multiply by 100. From £100 to £120: (120 − 100) ÷ 100 × 100 = 20% increase. The percentage-increase calculator on this site shows the working step by step.
How do I calculate a percentage decrease?
Subtract the new value from the original, divide by the original, multiply by 100. From £120 to £90: (120 − 90) ÷ 120 × 100 = 25% decrease. The percentage-decrease calculator does this with worked UK examples.
How do I calculate the percentage off a price?
Multiply the original price by (1 − discount ÷ 100). 20% off £80: 80 × (1 − 0.20) = 80 × 0.80 = £64. The discount calculator on this site handles stacked discounts ('extra X% off') correctly.
How do I calculate the percentage difference between two numbers?
Take the absolute difference, divide by the average of the two numbers, multiply by 100. Between 180 and 65: |180 − 65| = 115; (180 + 65) ÷ 2 = 122.5; 115 ÷ 122.5 × 100 = 93.88%. The percentage-difference calculator works for any two numbers.
Is this percentage calculator free?
Yes — every calculator on this site is free, with no signup. The site is funded by ads (UK GDPR-compliant) and uses zero personal data beyond what your browser already sends. UK 2026/27 tax bands and ONS / HMRC / Ofgem figures are kept current.
Why use the UK percentage calculator?
It uses pounds (£), HMRC 2026/27 tax bands, UK National Insurance bands, ONS CPI for inflation comparisons, Land Registry HPI for house-price calculations, and gov.uk-sourced figures. US calculators use $ and US tax bands — not directly applicable to UK pay rises, ISA limits or stamp duty.
How do I work out a pay rise as a percentage?
Divide the rise by your current salary, multiply by 100. From £35,000 to £36,750 = (36,750 − 35,000) ÷ 35,000 × 100 = 5%. The salary-increase calculator on this site shows the real take-home effect after UK income tax and NI — the net rise is usually less than the gross rise.
What is the percentage formula?
Three formulas cover most queries: X% of Y = (X ÷ 100) × Y; X is what % of Y = (X ÷ Y) × 100; % change from A to B = ((B − A) ÷ A) × 100. Each has its own dedicated calculator on this site with worked UK examples.
How accurate are the UK figures?
Tax bands are the official HMRC 2026/27 figures (income tax personal allowance £12,570; basic rate to £50,270; higher to £125,140). NI bands are 2026/27 Class 1 rates. Inflation calculations use ONS CPI. Pension allowance is the 2026/27 £60,000 figure. Sources are linked at the bottom of each calculator.