All PercentNinja Calculators
The PercentNinja calculator library brings together a complete set of free online percentage tools for everyday use, business calculations, and education. Whether you need to work out a discount, calculate VAT, measure percentage change, or analyse pricing and profit, these calculators provide fast and accurate results.
Each calculator is designed for real-world scenarios. Shoppers can calculate savings and sale prices, students can check homework or learn percentage formulas, and business users can analyse margins, markups, VAT, and pricing adjustments. All tools work with any currency or numeric value and include clear explanations so you understand how the result is calculated.
If you are modelling UK student finance and want a structured check on whether household income may have fallen enough to explore a current year income (CYI) reassessment, use the Student Finance CYI Calculator (guidance only—always confirm with Student Finance Wales or Student Finance England).
Every calculator page includes worked examples, simple formulas, and frequently asked questions to help you learn as you go. Browse the tools below to find the percentage calculator that matches your task, from basic percentage conversions to advanced pricing and business calculations.
Browse our complete collection of free percentage calculators. Each tool includes a clear explanation, worked examples, and FAQs so you can understand the answer (not just get a number).
What is X% of Y?
Calculate a percentage amount for discounts, VAT/tax amounts, tips, and commissions.
X is what percent of Y?
Find what percentage one number represents of another (scores, budgets, benchmarks).
Percentage Increase / Decrease
Measure growth or decline between an old value and a new value.
Add or Subtract a Percentage
Apply a percentage change directly to a single starting value.
Percentage Difference
Compare two numbers relative to their average (useful for comparisons).
Reverse Percentage
Work backwards to the original value before a percentage change or discount.
VAT Calculator
Add VAT, remove VAT, or calculate VAT amount only (UK-friendly).
Reverse VAT Calculator
Find the net price and VAT amount from a VAT-inclusive total.
Discount Calculator
Calculate final price after a percentage discount and see savings.
Sale Price Calculator
Find the discount percent when you know original price and sale price.
Markup & Margin Calculator
Cost to selling price + profit, with markup and margin explained.
Markup Calculator
Set selling price from cost and markup percentage.
Margin Calculator
Calculate profit margin from cost and selling price.
Markup vs Margin Converter
Convert markup % to margin % (and margin to markup).
Tip Calculator
Calculate tip amount, total, and per‑person split.
Percent ↔ Decimal Converter
Convert percentages to decimals and decimals to percentages.
Average Percentage Calculator
Calculate a simple average from multiple percentage values.
Percentage Change
Calculate percent increase/decrease from an old value to a new value.
Student Finance CYI Calculator
Compare prior household income with a current-year estimate for Wales or England (informational only).
Compound Percentage Change
Calculate repeated percentage growth/decline over multiple periods.
Percentage to Fraction
Convert a percentage (including decimals) into a simplified fraction.
Fraction to Percentage
Convert a fraction to a percentage using numerator and denominator.
Decimal to Percentage
Convert a decimal to a percentage (e.g. 0.125 → 12.5%).
Exam Percentage
Convert a score into a percentage (score ÷ total × 100).
Percentage Progress
Track percent complete towards a goal and see how much remains.
Percentage of Time
Work out what percent one time period is of another.
Cost From Margin
Find cost price needed to hit a target margin at a given selling price.
Compound Interest Calculator
Estimate future value with compounding and optional monthly contributions.
Simple Interest Calculator
Work out interest earned and final amount when interest is not compounded.
Savings Calculator
Project savings growth with a starting balance and regular monthly deposits.
Loan Interest Calculator
Estimate monthly repayment, total repayment, and total interest.
APR Calculator
Estimate annual percentage rate from repayment, term, and fees.
Investment Return Calculator
Measure gain, ROI, and return multiple from start value to finish value.
Percentage Reduction Calculator
Measure how much a value has fallen from an original amount.
Percentage Remaining Calculator
Find how much remains and the percentage left from a total.
Percentage of Total Calculator
Work out what share one part represents of the whole.
Weighted Percentage Calculator
Calculate weighted averages for grades, KPIs, and scorecards.
Percent Error Calculator
Measure percent error between estimated and actual values.
Break-even Calculator
Estimate break-even units based on fixed costs and contribution per unit.
Popular percentage question pages
Get instant answers to common percentage questions and then use the main calculator for any custom percentage problem.
What is 5 % of 50
Quick answer + step-by-step explanation for this percentage question.
What is 5 % of 80
Quick answer + step-by-step explanation for this percentage question.
What is 5 % of 100
Quick answer + step-by-step explanation for this percentage question.
What is 5 % of 120
Quick answer + step-by-step explanation for this percentage question.
What is 5 % of 500
Quick answer + step-by-step explanation for this percentage question.
What is 10 % of 50
Quick answer + step-by-step explanation for this percentage question.
What is 10 % of 80
Quick answer + step-by-step explanation for this percentage question.
What is 10 % of 100
Quick answer + step-by-step explanation for this percentage question.
What is 10 % of 120
Quick answer + step-by-step explanation for this percentage question.
What is 10 % of 250
Quick answer + step-by-step explanation for this percentage question.
What is 12 % of 50
Quick answer + step-by-step explanation for this percentage question.
What is 12 % of 75
Quick answer + step-by-step explanation for this percentage question.
Browse by hub
Which calculator should I use?
- Percentage of: “What is 20% of £150?” → Percent of a Number
- What percent: “£45 is what % of £60?” → What Percent is X of Y?
- Change over time: “£100 to £120” → Increase/Decrease
- Apply a change: “Add 10% to £200” → Add/Subtract
- Final price after discount: “£120 minus 15%” → Discount
- Original price before discount: “£80 after 20% off” → Reverse %
- VAT totals: “Add/remove VAT from a price” → VAT
- Student finance (CYI): “Has household income fallen enough to explore a reassessment?” → Current Year Income Calculator
Percent off discount pages
Quick guides for common sale headlines: the discount amount and the final price after a percentage off an original price—alongside discount and ecommerce tools below.
10% off 50
Discount amount and final price.
10% off 100
Discount amount and final price.
15% off 100
Discount amount and final price.
20% off 100
Discount amount and final price.
20% off 150
Discount amount and final price.
25% off 200
Discount amount and final price.
30% off 150
Discount amount and final price.
30% off 200
Discount amount and final price.
All calculators (by category)
Browse every tool on PercentNinja. These categories help you find the right calculator fast.
Pricing / Business
- Break Even Calculator
- Break-even Revenue Calculator
- Contribution Margin Calculator
- Price From Margin Calculator
- ROI Calculator
- Target Profit Calculator
- Gross Profit Calculator
- Net Profit Margin Calculator
- Profit Calculator
- Payback Period Calculator
- Break-even Price Calculator
- Break-even Revenue from Contribution Ratio
- Break-even Units from Revenue Target
- Contribution Margin Ratio Calculator
- Contribution per Unit Calculator
- Net Profit After Expenses
- Wholesale Price Calculator
Pricing
- Cost From Margin
- Discount Calculator
- Margin Calculator
- Markup Calculator
- Markup Margin
- Markup Vs Margin
- Sale Price
- Keystone Pricing Calculator
- Margin from Markup Calculator
- Markup from Margin Calculator
- Price Increase to Hit Profit
- Unit Profit Calculator
Pricing / Ecommerce
- Stacked Discount Calculator
- Platform Fee Calculator
- Stripe Fee Calculator
- Etsy Fee Calculator
- eBay Fee Calculator
- Amazon Fee Calculator
- Discount to Hit Margin
- Afterpay/Clearpay Fee Calculator
- Effective Discount Percentage
- Effective Fee Rate Calculator
- Klarna Fee Calculator
- Margin After Fees Calculator
- Marketplace Net Payout Calculator
- Packaging Cost Percentage
- PayPal Fee Calculator
- Refund Fee Impact Calculator
- Shipping Cost Percentage
- Square Fee Calculator
- Transaction Fee Calculator
- Unit Economics Calculator
Marketing
- ROAS Calculator
- CPA Calculator
- Ad Spend as % of Revenue
- Break-even ROAS Calculator
- CPC Calculator (Cost Per Click)
- CPM Calculator (Cost Per 1,000 Impressions)
- CTR Calculator (Click-Through Rate)
- eCPM Calculator
- Max Ad Spend for Target ROI
- Maximum CPA Calculator
VAT
- Reverse Vat
- Vat Calculator
- VAT from Gross
- VAT from Net
- VAT Rate Calculator
- Flat Rate vs Standard VAT
- Import VAT Calculator (Estimate)
- Margin on VAT-Inclusive Price
- Price After Discount and VAT
- Quarterly VAT Estimator
- Reverse VAT (Custom Rate)
- VAT Flat Rate Calculator (UK FRS)
- VAT Impact on Price Calculator
- VAT Margin Scheme Calculator
- VAT on Discounted Price
- VAT on Services Calculator
- VAT Portion of Total
- VAT Rate Change Impact
- VAT Reclaim Calculator
- VAT Threshold Remaining (UK)
Finance / Growth
- Compound Interest Calculator
- Simple Interest Calculator
- Savings Calculator
- Investment Return Calculator
- Loan Interest Calculator
- APR Calculator
- CAGR Calculator
- How to Calculate Compound Interest
Growth / Finance
Salary / Income
- Commission Calculator
- Pay Rise Calculator
- Student Finance CYI Calculator
- Household Income Drop Calculator
Basic %
Basic % / Change
Basic % / Comparison
Basic % / Reverse
Conversions
Stats / Utility
Utility
- Exam Percentage
- Percentage Of Time
- Percentage Progress
- Percentage Reduction Calculator
- Percentage Remaining Calculator
- Percentage of Total Calculator
- Weighted Percentage Calculator
- Percent Error Calculator
- Tip Calculator