CalcPlanet offers 725+ free online calculators and tools across finance, health, math, science, conversions, and everyday life. Use our BMI calculator, mortgage calculator, percentage calculator, loan EMI calculator, tip calculator, currency converter, salary to hourly converter, discount calculator, sales tax calculator, and hundreds more — all instant, mobile-friendly, and require no sign-up. Whether you need to calculate body mass index, monthly mortgage payments, percentage change, compound interest, calorie intake, unit conversions, or crypto prices, CalcPlanet provides accurate results with transparent formulas and step-by-step explanations. Our growing library of free calculators is trusted worldwide for finance planning, fitness tracking, academic study, engineering, cooking, travel, and small business. Explore curated guides, real-world examples, and formula references to learn how each calculation works. Browse popular categories: BMI calculator, percentage calculator, mortgage calculator, tools, all calculators, guides, formulas, finance, health, math, conversion, and about CalcPlanet. Free calculators, instant answers, no ads in core results, accurate every time.
Percentages show up everywhere — in discounts, interest rates, tax bills, test scores, and investment returns. The problem is that even people who are confident with numbers often pause to double-check their percentage math. This free percentage calculator eliminates that pause. It handles the five most common percentage problems in seconds: finding X% of a number, expressing one number as a…
The calculator covers all five core percentage modes in one tool. Select your mode, enter the values, and the result appears immediately — along with the full calculation so you can verify the logic. This is especially useful for quick decisions: checking whether a 'sale' price is actually a good deal, verifying the VAT amount on an invoice, confirming a grade percentage before a test result is official, or spotting whether a quoted interest rate is monthly or annual.
Percentage arithmetic has three basic forms. Finding a part of a whole (e.g. 15% of $240 = $36) uses multiplication. Expressing a part as a percentage of a whole (e.g. 36 is what % of 240 = 15%) uses division. Calculating change between two values (percentage increase or decrease) compares the difference to the original. All three are handled here — just pick the mode that matches your question.
A common mistake is confusing 'percentage points' with 'percent change'. If an interest rate rises from 4% to 5%, that is a 1 percentage-point increase, but it is a 25% increase in the rate itself. The percentage change mode in this tool calculates the relative change, which is what matters most for financial comparisons.
Reach for this calculator whenever the mental arithmetic isn't reliable enough to act on — when verifying a quoted discount before purchase, calculating a tip accurately at a restaurant, working out whether a salary increase keeps pace with inflation, or checking whether a tax rate has been applied correctly to an invoice. It is equally useful for students checking exam-percentage calculations, teachers converting raw marks, and anyone building a spreadsheet who wants to verify a cell formula before relying on it.
The single most common error is confusing percentage points with percent change. A rate rising from 4% to 5% is a 1 percentage-point increase, but a 25% relative increase — and these two numbers are not interchangeable. A second frequent mistake is applying a percentage reduction twice: 'get 20% off, then another 10% off' is not a 30% reduction; the second 10% applies to the already-reduced price, producing an 28% combined discount. Use this calculator to verify the actual result before assuming.
A retailer marks a £85 jacket down by 35% for a sale — the actual saving is £29.75, giving a sale price of £55.25. A student scores 68 out of 85 on a test — that's 80%, not the 68 the raw mark suggests. A business owner sees revenue grow from £120,000 to £153,600 — a 28% increase, not the £33,600 absolute figure. In each case, the percentage gives the comparable, scalable figure that the raw number does not.
Three core percentage formulas cover every common use case
Part = Whole × (P ÷ 100) | P = (Part ÷ Whole) × 100 | Change% = ((New − Old) ÷ Old) × 100
Formula 1 finds a value (e.g. 15% of $200 = $30). Formula 2 expresses a part as a percentage (e.g. $30 is 15% of $200). Formula 3 measures relative change between two values (e.g. price from $200 to $230 = +15%).
A software subscription is
Result: Final price: $98.40 — you save $21.60 (18% discount verified)
Select 'X% of Y', enter X = 20 and Y = 350. The calculator returns 70. The formula is: 350 × (20 ÷ 100) = 70. Alternatively, divide 350 by 5, since 20% = 1/5.
Select 'Percentage change', enter the original value first, then the new value. The formula is: ((New − Old) ÷ Old) × 100. For example, a salary going from $50,000 to $55,000 is a 10% increase.
Percentage change is the relative difference between two values. Percentage points measure the arithmetic difference between two percentages. If a tax rate rises from 20% to 25%, that is 5 percentage points — but a 25% relative increase in the rate.
Use 'X is what % of Y' in reverse. If a discounted price is $60 and the discount was 25%, the original was $60 ÷ (1 − 0.25) = $80. Our reverse percentage calculator handles this directly.
Interest rates on loans and savings accounts, VAT and sales tax, investment returns, salary increases, and price discounts are all expressed as percentages. Understanding how to move between a percentage and an actual monetary amount is one of the most useful everyday maths skills.
Free, fast, and easy. Use 722 calculators and 108 tools. No sign-up. Get instant results for math, money, health, and more.
By CalcPlanet Editorial · · According to our Editorial Standards and Formula Sources, every calculator is reviewed before publication.
CalcPlanet calculators are free, privacy-first, and formula-reviewed.
Editorial Standards · Formula Sources · Privacy · Terms · Contact
