Definition
Customer effort score (CES) measures how easy it was for a customer to do something: get a problem solved, finish onboarding, complete a purchase. It's usually a single question after the task, such as "How easy was it to…?" on a scale.
Formula
A common form: CES = average score on a scale (for example 1 to 7), or the share of customers answering "easy" or better.
Why it matters
Effort predicts loyalty well: customers who struggle are more likely to leave even if the problem was solved.
Pair it with behaviour
Survey answers tell you how people felt; events show where the effort was. Compare CES with the steps and time it took in the product, such as failed attempts and repeated actions, to find what to simplify.