Lazy marketers love this page.

As online marketers, we have to deal with numbers a lot. To identify lucrative ads, to calculate conversion rate changes, or to evaluate the ad spend per customer.

And yes, it happens to most of us: We don’t have all the formulas and calculations ready in our brains at any time.

That’s why I gathered the most important formulas here. So you can shine with stellar knowledge in percentage calculation. Even if you are having one of these blockhead days.

You are welcome.


Pro tip for smart marketers:

Add this page to your browser’s bookmarks / favourites. I update this page frequently.


Table of contents:


Conversion rate formulas

Calculate conversion rate

Formula: goal completions / visitors x 100 = conversion rate
Example: 50 form submits / 500 visitors x 100 = 10% conversion rate

Calculate your conversion rate:

Please note that Google Analytics calculates conversion rates with number of sessions, not number of users.

Conversion rate = %

Calculate change in conversion rate

Formula: ( new conversion rate / old conversion rate - 1 ) x 100 = conversion rate change
Example: ( new conversion rate 9 / old conversion rate 7 - 1 ) x 100 = 28.57% conversion rate change

Calculate your change in conversion rate:

Change in conversion rate = %
Conversion rate multiplied by: x


Performance & finance formulas

Calculate cost per actioncost per lead (CPL), cost per order (CPO),cost per click (CPC), cost per acquisition (CPA), etc.

Formula: marketing or ad spend / actions = cost per action
Example: $5000 marketing spend / 132 orders = $37.88 cost per order

Calculate your cost per action:

Cost per action = $
Can be any currency, obviously.

Calculate return on advertising spend (ROAS)

Formula: ( revenue from ads - ad spend ) / ad spend * 100 = return on advertising spend
Example: ( $1,100 revenue from ads - $1,000 ad spend ) / $1,000 ad spend * 100 = 10% return on advertising spend

Calculate your return on advertising spend (ROAS):

Return on advertising spend (ROAS) = %

Calculate return on investment (ROI)

Formula: ( revenue - investment ) / investment * 100 = return on investment in %
Example: ( $10000 revenue - $5000 invested capital ) / $5000 invested capital * 100 = 100% return on investment

Calculate your return on investment (ROI):

Return on investment (ROI) = %

Calculate change in revenue

Formula: ( revenue in period b or ab test variation / revenue in period a or ab test control - 1 ) x 100 = revenue change
Example: ( $12000 revenue in period b / $10000 revenue in period a - 1 ) x 100 = 20% revenue change

Calculate your change in revenue:

Change in revenue = %
Revenue multiplied by: x


Bounce & engagement formulas

Calculate bounce rate

Formula: visits without engagement / total visits * 100 = bounce rate
Example: 120 visits without engagement / 360 total visits * 100 = 33.33% bounce rate

Calculate your bounce rate:

Bounce rate = %

Calculate change in bounce rate

Formula: ( new bounce rate / old bounce rate - 1 ) x 100 = bounce rate change
Example: ( new bounce rate 7 / old bounce rate 14 - 1 ) x 100 = -50% bounce rate change

Calculate your change in bounce rate:

Change in bounce rate = %
Bounce rate multiplied by: x

Calculate engagement rate

Formula: visits with engagement / total visits * 100 = engagement rate
Example: 1500 visits with engagement / 10000 total visits * 100 = 15% engagement rate

Calculate your engagement rate:

Engagement rate = %

Calculate change in engagement rate

Formula: ( new engagement rate / old engagement rate - 1 ) x 100 = engagement rate change
Example: ( new engagement rate 50 / old engagement rate 40 - 1 ) x 100 = 25% engagement rate change

Calculate your change in engagement rate:

Change in engagement rate = %
Engagement rate multiplied by: x


Growth marketing formulas

Calculate product virality

Product virality is a complex topic. The calculator below suggests that you have a product where customers can invite other people to use the product, too.

Formula: number of customer base x ( number of invitations each customer shares x conversion rate of each invitation ) = number of new customers
Example: cusomter base of 4000 x ( 15 invitations per customer x 5% invitation conversion rate ) = 3000 new customers

Calculate your product virality:

New customers:
Viral coefficient:

The viral coefficient has to be 1 or higher to achieve true virality. With a viral coefficient >1, your product will spread and generate more and more new customers continuously while you sip your Espresso Martinis. Oh, and: Yes, that’s hard.

Calculate customer retention rate

Formula: ( customers at end of period - customers acquired in period ) / customers at start of period x 100 = retention rate
Example: ( 210 customers on January 31st - 10 customers acquired in January ) / 205 customers on January 1st x 100 = 97.56% retention rate

Calculate your customer retention rate:

Customer retention rate = %

Calculate customer churn rate

Formula: lost customers in period / customers at start of period * 100 = churn rate
Example: 20 lost customers in Q4 / 1000 customers at start of Q4 * 100 = 2% churn rate

Calculate your customer churn rate:

Customer churn rate = %