Free Percentage Calculator
Six standard percentage calculations, plus a marketing-metrics section for ROAS, conversion lift, margin, CTR, CPC and CPM. Free, no sign-up, runs entirely in your browser.
Percentage Calculations
What is X% of Y?
X ÷ 100 × YX is what % of Y?
(X ÷ Y) × 100Percentage change from X to Y
((Y − X) ÷ X) × 100Add X% to Y
Y + (X ÷ 100 × Y)Subtract X% from Y
Y − (X ÷ 100 × Y)If Y is X% of something, what is the something?
Y ÷ (X ÷ 100)Marketing Metrics
The percentage calculations marketers run all day. Plug your numbers in and get ROAS, conversion rate, conversion lift, margin, markup and ad-platform metrics in one place.
ROAS — Return on Ad Spend
For every £1 you spend on ads, how much revenue does it bring back?
Revenue ÷ Ad spend · A ROAS of 4:1 means £4 of revenue for every £1 spent.Conversion rate
What percentage of visitors completed your goal action?
(Conversions ÷ Sessions) × 100Conversion lift (uplift)
The percentage improvement between two conversion rates. Useful for A/B test results.
((New − Old) ÷ Old) × 100 · This is the relative lift, not the absolute difference in percentage points.Profit margin
The percentage of revenue you keep as profit after costs.
((Revenue − Cost) ÷ Revenue) × 100Markup
The percentage added to cost to get the selling price. Often confused with margin — they are not the same.
((Price − Cost) ÷ Cost) × 100CTR, CPC and CPM
Enter ad spend, impressions and clicks to get all three at once.
Free online percentage calculator
A percentage calculator handles all the everyday percentage maths most people need: working out what X% of a number is, finding what percentage one number is of another, calculating percentage change, and adding or subtracting a percentage from a value. This free online percentage calculator from The Digital Maze covers all six common percentage calculations on one page, with formulas shown for each one. Everything runs in your browser. No sign-up, no ads.
The marketing-metrics section below the standard percentage calculators handles the calculations marketers run every day: ROAS, conversion rate, conversion lift, profit margin, markup, and the three core ad-platform metrics (CTR, CPC, CPM).
How to calculate a percentage
What is X% of Y?
The most common question. Divide X by 100, then multiply by Y. So 15% of 200 is (15 ÷ 100) × 200 = 30.
X is what % of Y?
Divide X by Y, then multiply by 100. So 30 is (30 ÷ 200) × 100 = 15% of 200.
Percentage change
How much something has gone up or down. Subtract the old value from the new, divide by the old, multiply by 100. Going from 100 to 130 is a 30% increase. Going from 130 to 100 is a 23% decrease.
Add or subtract a percentage
To add 20% to 100: calculate 20% of 100 (= 20), then add it (= 120). To subtract 20% from 100: same but subtract (= 80). VAT, discounts and price changes are usually one of these two.
Marketing metrics explained
ROAS
Return on Ad Spend. Revenue ÷ ad spend. A ROAS of 4:1 means every £1 of ad spend generated £4 of revenue. Not the same as ROI (which accounts for cost of goods, fulfilment, etc).
Conversion rate
The percentage of sessions or clicks that ended in a conversion (purchase, lead, sign-up). The biggest single number any ecommerce or lead-gen site has. Improving CR by even half a percentage point usually pays for the SEO or CRO work that achieved it many times over.
Conversion lift
The relative improvement between two conversion rates. Going from 2.5% to 3.2% is a 28% lift, not a "0.7%" improvement. This catches people out constantly. The relative lift is what matters when you are reporting test results.
Margin vs markup
Margin is profit as a percentage of revenue. Markup is profit as a percentage of cost. Sell a £60 product for £100 and the markup is 67% but the margin is 40%. Mixing them up is one of the most common pricing mistakes.
CTR
Click-Through Rate. Clicks ÷ impressions × 100. The percentage of people who saw your ad or search result and clicked through. Higher CTR means your creative or messaging is working.
CPC and CPM
Cost Per Click (spend ÷ clicks) and Cost Per Mille (spend ÷ impressions × 1000, the cost of 1,000 ad impressions). Different platforms optimise for different things. Search and shopping campaigns usually report CPC; display and awareness campaigns usually report CPM.
Margin vs markup, the example that catches everyone out
Buy a product for £60. Sell it for £100. The profit is £40.
- Markup (profit as a percentage of cost): £40 ÷ £60 = 66.67%.
- Margin (profit as a percentage of revenue): £40 ÷ £100 = 40%.
Same money, different number. Which one your finance team uses, and which one your sales team uses, are often two different things. Worth standardising across the business.
Common percentage calculation use cases
- VAT. UK VAT is 20%. Add 20% to a net price to get the gross. Subtract one-sixth from a gross to get the net. (Not 20% — divide by 1.2 instead).
- Discounts. "20% off £80" means £80 − (20% of £80) = £80 − £16 = £64.
- Tips and service charges. 12.5% of £45 = £5.63.
- Growth rates. Revenue went from £150,000 to £180,000? That is a 20% increase.
- Conversion improvements. See the conversion lift calculator above.
- Margin pricing. Selling at a £60 cost with a 40% margin? Your selling price needs to be £100 (use the reverse percentage calculator).
Need help with marketing measurement?
If you are calculating ROAS, conversion lift or margin to track marketing performance, our GA4 and analytics team can help you build the tracking and reporting infrastructure that surfaces these numbers properly. Our PPC team works to a hard ROAS or CPA target on every account. Get in touch for a no-pressure conversation.