Math Calculators
Browse our collection of free online math calculators — built to solve the most common everyday maths problems instantly. Whether you need to calculate a percentage, work out a discount, or find a price increase, our tools give you fast, accurate answers with step-by-step explanations. No sign-up, no downloads — just instant results.
Our Free Math Calculators
- Percentage Calculator — Find percentages, percentage change, and percentage of a number
- Percentage Increase Calculator — Calculate the % growth between two numbers
- Percentage Decrease Calculator — Calculate the % drop between two numbers
- Discount Calculator — Find the sale price after any percentage discount
- ROI Calculator — Calculate return on investment as a percentage
How to Calculate a Percentage
Percentages are one of the most common calculations in everyday life. To find what percentage one number is of another, divide the part by the whole and multiply by 100. For example, to find what percentage 45 is of 180: (45 ÷ 180) × 100 = 25%. Our Percentage Calculator does this instantly for any values you enter.
Percentage Formulas at a Glance
| Formula | Use Case | Example |
|---|---|---|
| (Part ÷ Whole) × 100 | Find % of a total | 45 is 25% of 180 |
| ((New − Old) ÷ Old) × 100 | % increase or decrease | £80 to £100 = +25% |
| Original × (1 − Discount%) | Sale price after discount | £200 × 0.80 = £160 |
| (Gain ÷ Cost) × 100 | Return on investment | £50 profit on £200 = 25% ROI |
Why Use an Online Math Calculator?
Even simple maths can go wrong when you’re in a hurry — a misplaced decimal or forgotten step leads to the wrong answer. Our math calculators are built to be fast, accurate, and forgiving. Just enter your numbers and get the right answer instantly, with a clear explanation of how it was calculated. They’re used daily by students, teachers, shoppers, business owners, and professionals who need reliable answers without a spreadsheet.
Common Percentage Mistakes to Avoid
One of the most common errors is confusing percentage points with percentages. If an interest rate rises from 2% to 3%, that’s a 1 percentage point increase — but a 50% relative increase. Another mistake is applying a discount then a tax (or vice versa) and expecting the same result — the order of operations matters significantly. Our calculators handle these correctly every time.
Math Calculators for Students
Students use our percentage and ROI calculators for coursework, data analysis, and exam revision. The step-by-step answers show not just the result but how it was reached — making them a learning tool as well as a calculator. Whether you’re working through GCSE maths, A-Level statistics, or a university finance module, these tools support your studies without doing the thinking for you.
Math Calculators for Business
Business owners and finance professionals rely on accurate percentage calculations every day — for pricing strategies, margin analysis, discount structures, and investment performance. Our ROI calculator helps you quickly assess whether a project or campaign has delivered value, while the discount and percentage tools are essential for retail pricing and sales analysis.
Frequently Asked Questions
How do I calculate 20% of a number?
Multiply the number by 0.20. For example, 20% of 350 = 350 × 0.20 = 70. Alternatively, divide by 5. Our Percentage Calculator handles this instantly.
What is the formula for ROI?
ROI = ((Net Profit ÷ Cost of Investment) × 100). A £200 investment that returns £250 has an ROI of 25%. Use our ROI Calculator to calculate this in seconds.
How do I find the original price after a discount?
Divide the sale price by (1 − the discount rate). If an item is £160 after a 20% discount: £160 ÷ 0.80 = £200. Our Discount Calculator can reverse-calculate this for you.
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