Incrementality

Incrementality is the share of your sales that happened because of your advertising and would not have happened without it.

By Berend Vrakking, founder of Product Metrics. Updated 7 October 2026.

Formula

Incremental orders = orders from people who saw ads − orders from a comparable group who did not

Use two groups of the same size. Incremental ROAS is incremental revenue ÷ ad spend, so it counts only the sales the ads caused.

Example

Worked example, one test
Step	Value
Ad spend	€4,000.00
Orders from 10,000 people who saw ads	200
Orders from 10,000 comparable people who did not	150
Orders caused by the ads (200 − 150)	50
ROAS if all 200 orders are credited (200 × €80.00 ÷ €4,000.00)	4
Incremental ROAS (50 × €80.00 ÷ €4,000.00)	1

The ads were credited with €16,000.00 of revenue. Only €4,000.00 of it needed them; the rest would have turned up anyway. Credit says 4, cause says 1. Illustrative data.

For one product, and for an account

Some products are bought by people who already wanted them, and ads can take credit for those sales. Others are found through the ads. Incrementality is about that difference, and ROAS cannot show it, because ROAS counts every attributed sale, including the ones that would have happened anyway.

A test needs enough orders in both groups to show a difference, so a single product with few orders is hard to test on its own. Product Metrics is not an attribution tool and does not run incrementality tests. Its six segments are set by volume and attributed return, so read a segment’s return as attributed return, not as proof that the ads caused the sales.

Common mistake

Reading ROAS as if every attributed sale was caused by the ads. Attribution says which ad was credited, and only a comparison with a group that did not see the ads says what the ads added.

Questions

What is the meaning of incrementality?

It is the extra result your advertising caused: the orders, revenue or customers that would not exist without it.

How do you measure incrementality?

You compare a group of people or regions that saw your ads with a comparable group that did not, over the same period. The difference in orders or revenue between the two groups is the incremental result.

Is ROAS the same as incremental ROAS?

No. ROAS divides all the revenue credited to the ads by ad spend. Incremental ROAS divides only the extra revenue the ads caused by ad spend, so it is the same or lower.

Keep reading

Return on ad spend (ROAS)The ratio that counts all attributed sales, not only incremental ones.
Incrementality testing for Google ShoppingHow to set up a test and read what your ads added, step by step.
ROAS, MER, POAS and nCAC: which metric to useMER looks at total revenue against total marketing spend, so it does not depend on one platform’s attribution.
Last-click attributionOne way sales are credited to ads, which is not the same as causing them.
Break-even ROAS calculatorFind the return each product needs to break even.