The tool

The aim of surveylength is to provide an estimation of the median length of an online questionnaire.

Lower and Upper estimates

As it is very unlikely to get an estimate precise to the second, the lower and upper estimates around the estimated length indicate that in all probability, the length of your survey should range between these two estimates.


In this section you have to describe the structure, age and language of the respondents who will answer the survey.

Age of the respondents

By default, the percentage of respondents in each age category is fixed to 12.5%. You can modify this repartition according to the age structure of the respondents you need for your study.

Number of respondents

The number of respondents who are going to take part in your survey has an influence not on the average estimated length of your survey, but on the lower and upper estimates of this duration. The more respondents, the smaller the time interval around the estimated length


Percent of respondents by path

Many surveys contain « filter questions », which means than some respondents will have to answer more or less questions than others to reach the end of the survey. For example, only respondents who gave a low answer to a satisfaction question may be asked to explain why they are unsatisfied. In order to deal why such « filter questions », you have the possibility to indicate up to 3 different paths that respondents may have to follow. A path corresponds to a defined number of questions respondents will have to answer.

For example, within the same survey, 70% of your respondents may have to answer on average 10 single closed-ended questions and 1 open-ended question (= path 1), and 30% may have to answer on average 20 single closed-ended questions and 3 open-ended questions (= path 2). You can therefore indicate that 70% of your respondents will have to go through path 1, and 30% will have to go through path 2.

Type of questions

Here you have to indicate for each question type how many questions of that type are to be found in each path of your questionnaire.

Single closed-ended questions

Single closed-ended questions are all types of questions where respondents have to choose one or several answers in a predefined set of answers.  

Examples of single closed-ended questions:

On a scale from 1 to 9, how satisfied are you with your purchase?

Matrix table questions

Matrix table questions are used when respondents have to answer several questions using the same answer scale.

Examples of matrix table questions:

How satisfied were you with the following aspects of the service? (scale from 1 "not at all satisfied" to 5 "completely satisfied")

- Speed of resolution

- Knowledge of representative

- Solution offered

- Friendliness of representative

For this question type, you have to indicate the total number of items/question that respondents have to answer within all matrix tables. In this example, the number of items/questions respondents have to answer is 4.

Questions with multiple choices

A question wit multiple choice is a simple, closed-ended question type that lets respondents select one or multiple answers from a defined list of choices.

Ranking questions (drag-n-drop/drag-ranking, click-ranking)

A ranking question asks respondents to compare items to each other by placing them in order of preference.

Open-ended questions

An open-ended question is a question that respondents have to answer by using (and writing) their own words.

Examples of open-ended question:

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Pages with text only

Sometimes respondents have to read a text before or instead of answering a question. To estimate how long respondents need to read a text, count the number of words the text contains and enter the result in "text 1, number of words". (A quick way to count the number of words of a text is to copy and paste the text in a word document.)

Personalized questions

Certain complex questions may necessitate more time to answer. For example, respondents may have to watch a short movie, they may have to read a long text first, make a complicated calculation, etc.

It is difficult to estimate the time needed to answer such questions without knowing the question itself. If you want to take such questions into account in your estimation, go through the following two steps:

1/ indicate in “type 1: number” how often respondents will have to answer this or a similar question. 

2/ indicate in “type 1: duration” your best estimate of the time respondents will take to answer this question. 

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