Calculators and quizzes are decision-making tools that accept information from users and generate personalized outputs based on their circumstances. Depending on the output they provide, there are 3 types of calculators and quizzes.

A time zone calculator as an example of "Conversion" calculators, a fertility predictor as an example of a "Prediction" calculator, and a skin care routine recommendation as an example of a "Recommendation" calculator.
Calculator and quiz tools generally fall into one of three categories: conversion, prediction, or recommendation.

For the sake of simplicity, we refer to both calculators and quizzes as “calculators” throughout this article.

In This Article:

Conversion Calculators

Conversion calculators translate user inputs from one format to another. On their own, these tools don’t attempt to tell the user what they should do or interpret outputs for them. They help users accomplish tasks or better understand their situation.

For example, a carbon-footprint calculator asks users a series of questions about their daily habits. Then, it converts the information into a carbon-footprint score.

Carbonindependent.org: One UK-based carbon-footprint calculator asked many questions about daily consumption habits and converted the information into a carbon-footprint score, which could be compared to average scores from other parts of the world.

Conversion calculators can facilitate comparison between options by converting inputs into common terms. They enable users to compare “apples to apples.”

For example, a loan-comparison calculator can accept the details of multiple loans that are difficult to compare on their own and convert them into the same terms, such as the total amount and the monthly payments.

The details of two loans with different details that have been converted into comparable terms.
NerdWallet: This loan-comparison calculator converted loan details such as total amount, loan term, and interest rate into comparable monthly and total costs to facilitate comparison on meaningful terms.

Design Tip

Frame the outputs of a conversion calculator in ways that make sense to the user. The tasks users try to accomplish with the calculator should inform how the outputs are presented. For example, the following calculator compares time zones across the world. Normal working hours are highlighted in yellow, morning and evening hours in light blue, and nighttime hours in dark blue. These highlights make it easy to find a convenient meeting time for people in different places.

Four different timezones lined up next to each other to show what time it is in each timezone over a 24-hour period.
✅ World Time Buddy: Hours of the day in each time zone were highlighted in different colors; this design made it easy to find a meeting time for people in different locations.  

Prediction Calculators

Prediction calculators help users estimate the future. Users do not generally question the accuracy of the predictions if they trust the website providing the calculator. (They don’t know how to question the calculator’s algorithm because they don’t understand it themselves — hence, the use of the calculator.)

An ovulation calculator is an example of a prediction calculator. Users can indicate when their last period began and the average length of their cycle to see a predicted window of fertility.

A calendar that allows users to indicate their last period to predict their next fertile window.
This ovulation calculator predicted a window of fertility based on the user’s most recent period and average cycle length.

The simpler the calculator, the more likely users are to challenge the outputs. When users in our study interacted with complex tools, like investment calculators that predict average market returns over time given custom investment patterns, users did not challenge the outputs.

Design Tip

Designers are responsible for giving users accurate information because they might be helping naive or vulnerable user populations make decisions.

Recommendation Calculators

Users turn to recommendation calculators for advice. They are aware that calculator recommendations are not entirely altruistic. However, the allure of dumping disorganized information into the calculator and getting a personalized recommendation is powerful enough that users generally take the outputs seriously.

The homepage of the Mint Mobile website with a button to take their quiz at the bottom.
Mint Mobile: Users quickly utilized the Quiz for recommending phone plans on the homepage of Mint’s website when asked to find a plan that would meet their needs.

For example, we asked research participants to investigate whether Mint Mobile had any wireless phone plans that fit their needs. Participants quickly jumped into a quiz on the homepage to get recommendations for the best plan based on their circumstances. The quiz asked questions such as:

  • How many lines do you currently have?
  • How much data do you generally use?
  • Is your phone paid off?
  • How frequently are you connected to WiFi?

Overall, participants seemed to trust the quiz’s outputs as much as, if not more than, their own judgment.

“I would be interested in this quiz to see what they can offer. [...] The process is really fun and interactive. [...] It was kind of interesting picking a plan based on your usage and based on how you utilize data.”

Design Tip

Consider a recommendation calculator in workflows where users face decisions they are unprepared for. These calculators are seen as welcome guidance when users are feeling stuck and don’t know what options would best meet their needs.

Combining Calculator Types

Conversions and predictions can pave the way for recommendations because users often need to make decisions after seeing these types of results.

For example, a retirement calculator can help someone predict how much money they will have in retirement if they continue their current financial trajectory. This output creates the right opportunity for an organization to recommend methods to achieve the desired retirement goals.

A retirement calculator accepting details about demographics and spending to predict retirement savings.
AARP’s retirement calculator both predicted what someone will have saved by the time they retire and recommended changes to spending and saving habits to achieve the goal they have described.

Design Tip

Determine how the user will use the output of the calculator: the decisions that need to be made, the actions that are likely to follow, and the further questions — particularly in the case of conversion and prediction calculators. This information will reveal opportunities to recommend a course of action that would benefit both the user and the business.

A calculator accepting a user's ACT or SAT score and converting it to the other type.
✅ Compass Education Group: This concordance calculator helped students convert their university-admission test scores from one test type to another (ACT or SAT) and suggested which test they ought to prioritize given their score. The combination of the conversion and recommendation addresses the fundamental questions that likely brought many students to this calculator in the first place.

Keep calculator outputs and recommendations simple, neutral, and available. Do not force users to subscribe to anything to receive the useful information they seek after using a calculator. Users find calculators most useful when they attempt to be helpful without forcing commitment.

Conclusion

Users with a lot of experience at a task will not need a calculator to help them with that task. Conversion, prediction, and recommendation calculators serve inexperienced users who feel lost and are looking for guidance they can trust.