Form calculations and variables

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Video tutorial

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How it works

Calculations in Fillout forms let you compute values and respondent input, and display them. They are built using step-by-step rules rather than a single formula. For example, let’s calculate the total cost of a chicken wings order based on quantity.

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Interactive demo

Each rule performs one operation, and the result is passed to the next rule in sequence. For example, instead of writing “(A + B) x C” in one line, you would break it down into separate rules:

• Rule 1: Start with A (initial value = @FieldA) and Add @FieldB
• Rule 2: Take the total from Rule 1 and multiply by @FieldC

Each step is processed in order, which ensures the final result is calculated correctly. Each rule takes one value. If you put several references in one value box, like @A + @B, Fillout reads it as text and skips the rule. Add a separate rule for each field instead. A rule with an empty value is skipped too, so it doesn’t count as 0. When the result is shown in the form, it follows this display format by default:

• Values are rounded to 2 decimal places
• Trailing zeros are not displayed (e.g. 10.2 not 10.20)
• No currency symbols or thousands separators are added

To keep trailing zeros or round to a different number of places, such as whole numbers, set Decimal places when you add the calculation.

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Add a calculation

By opening the Logic modal, you can create calculations to compute values dynamically based on static values or previous respondent input. Let’s add calculations to an order form. Build calculations with AI You can also ask Form Agent to help you create calculations for your form. Learn more here.

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Combine calculations

Each rule does one operation, so a formula like (A × B) + (C × D) needs more than one calculation:

1. Add a Number calculation that starts from A and has a rule that will multiply by B.
2. Add a second Number calculation that starts from C and has a rule that will multiply by D.
3. Add a third Number calculation. For its Initial value, click the plus icon, then the calculator icon, and pick the first calculation. Add a rule that will add the second calculation.

Show the third calculation on your form. A calculation can use other calculations this way, so you can build up longer formulas, like a price that adds several items.

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Calculate a percentage

Add a Number calculation that starts from the value. Add a rule that will divide by the total, then another that will multiply by 100. Turn on Always for both rules so they run every time. For example, for a 10-question quiz, start from Correct answers, divide by 10, then multiply by 100. A respondent with 7 correct answers gets 70.

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Rule hierarchy for results

To resolve conflicts between rules, results follow a clear priority order. Higher-priority rules always take precedence over lower-priority ones.

• A always wins (Highest priority): All A rules take precedence over every other rule.
• B always wins after A: Applies after A. B rules are overridden when they conflict with A.
• C always wins after B: Applies after A and B. C rules are overridden when they conflict with A or B.
• D only wins when the others don’t (Lowest priority): Only applies when none of the higher-priority rules (A, B, or C) apply.

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Dynamic calculation

Make the price dynamic After adding a payment page, type @ or click the plus icon and click the calculator icon to reference a calculation. Now, the price will change depending on the customer’s order. Display dynamic calculation results in your form On a heading or paragraph field, you can type @ and click the calculator icon to reference previous answers or calculations. You can style this text by highlighting it and changing the font size, weight, or color. Pre-fill fields with calculations To pipe calculations as input, open the field’s settings . Under Default value, click the plus icon followed by the calculator icon to reference a calculation.

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Calculate the time between dates or times

Use a Duration calculation to work out someone’s age, how long a trip lasts, or how many hours someone worked. Pick the Start and End questions, then the Units you want the result in: years, months, weeks, days, hours or minutes. For Start or End, you can also click the calendar icon and pick a date utility, like Today or Submission time. For example, start from a date of birth and end on Today to get someone’s age. The result is always a whole number, rounded down. For example, from 1:00 PM to 4:30 PM in hours gives 3, not 3.5.

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Get hours with decimals, or take off a break

For a timesheet, you might want 3.5 hours instead of 3, or to take off a lunch break. A Duration calculation can’t do that on its own, so add a second calculation that does the math:

1. Add a Duration calculation in minutes. From 1:00 PM to 4:30 PM, it gives 210.
2. Add a Number calculation. For its Initial value, pick the Duration calculation.
3. If you ask for a break, click + New rule, choose subtract and pick the break question. With a 30-minute break, that leaves 180.
4. Click + New rule again, choose divide by and enter 60. 210 minutes becomes 3.5 hours, or 3 hours with the break.
5. Show the Number calculation on your form, not the Duration one.

To check it, click Preview and enter 1:00 PM and 4:15 PM, with no break. You should see 3.25.

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Add days to a date

Calculations can’t add days, weeks or months to a date, so they can’t work out a due date or an end date. A calculation can be Text, Number or Duration, and none of them gives a date as its result. A Duration calculation only measures the time between two dates or times. To show a date a set number of days from today, set a date field’s Default value to N days from now instead. See Pre-fill dates in your form.

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Other things calculations can’t do

• Take part of an answer, like a first name from a full name. A Text calculation can only set a value.
• Generate random values or number respondents, like Respondent 1, 2, 3. Forms can’t see how many submissions they already have. Each submission gets a unique Submission ID instead.
• Show a clickable link. A Text calculation shows as plain text. To send respondents to a link from a calculation, add a URL button to the ending page and reference the calculation in its URL. You can also select text in a Paragraph, add a link, and type @ in its URL to insert the calculation.

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Pre-fill fields with a calculation

Much like how fields are pre-filled elsewhere in Fillout, you can reference calculations there as well.

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Calculate quiz scores

Fillout automatically computes the score and lets you display it on any page you prefer. Additionally, you can use weighted scoring, which also lets you assign results based on total score.

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