Formula

Formulas are the configurator's most powerful tool. With them you calculate prices, dimensions, weight, a product number or display values dynamically from your customers' input – such as "price = area × square-metre price" or "10% discount from 100 units".

This chapter explains formulas from the ground up. You need no programming knowledge – just a bit of logical thinking. You can use all examples directly.

Premium feature: "Expert calculation" (all formula inputs) is part of the Premium version. In other versions the formula fields are visible but disabled – see Advanced & Premium version.

What is a formula?

A formula is a small calculation expression that produces a result. In the simplest case it is pure maths:

price + 10

This formula means: take the product price and add 10. Instead of fixed numbers you can use variables – placeholders that are filled with the real values of the customer input at runtime.

Technical background: formulas use the template language Twig in a secured environment. Only the variables, functions and filters documented here are allowed – this keeps formulas safe.

Where do I enter formulas?

There are two places:

1. Configurator calculations (the configurator's Calculation tab). Each calculation has a switch and a formula field:

Calculation	Result	Variable type
Price	Final unit price	Number
Width / Height / Length / Weight	New dimension/weight value	Number
Product number	Generated product number	Text

2. Field calculations (the Calculation tab of an individual field):

Calculation	Result	Variable type
Default value	Pre-fill of the field	Number/Text
Result formula (only field type Interim result)	Live displayed value	Text

Available variables

In every formula you have these variables available:

Variable	Meaning
`price`	Base unit price of the product
`width`, `height`, `length`, `weight`	Dimensions and weight of the product
`fields.<identifier>`	The current value of a field, e.g. `fields.quantity`
`options.<identifier>.price`	Surcharge of the selected option of that field
`options.<identifier>.width`	Width of the selected option (likewise `height`, `length`, `weight`)
`options.<identifier>.value`	Technical value of the selected option

<identifier> is the technical identifier of the field (see Elements & field types).
For multiple choice, options.<identifier> refers to the first selected option.
Fields without input return an empty value – use the default filter for those (see below).

Calculating: operators

Operator	Meaning	Example
`+` `-` `*` `/`	Basic arithmetic	`price * 2`
`%`	Remainder (modulo)	`fields.quantity % 2`
`**`	Power	`width ** 2`
`~`	Concatenate text	`'NR-' ~ fields.colour`
`==` `!=` `>` `<` `>=` `<=`	Comparisons	`fields.quantity >= 100`
`and` `or` `not`	Logical combination	`width > 0 and height > 0`

Important: To join text use ~, not +. When calculating, use the dot as the decimal separator (1.5, not 1,5).

Functions & filters

Functions (called with parentheses):

Function	Meaning	Example
`max(a, b, …)`	largest value	`max(price, 25)`
`min(a, b, …)`	smallest value	`min(price, 500)`
`round(value, digits)`	round	`round(price, 2)`

Filters (applied with |):

Filter	Meaning	Example
`round`	round	`price\|round(2)`
`ceil`	round up	`(price)\|ceil`
`floor`	round down	`(price)\|floor`
`abs`	absolute (positive) value	`price\|abs`
`number_format`	format	`price\|number_format(2)`
`default`	fallback when empty	`fields.quantity\|default(1)`
`length`	count/length	`fields.lines\|length`

abs, ceil and floor exist only as filters (value|abs), not as functions.

Conditions and intermediate variables

You can use case distinctions and your own intermediate values:

{% if fields.quantity >= 100 %}
    price * 0.9
{% elseif fields.quantity >= 50 %}
    price * 0.95
{% else %}
    price
{% endif %}

{% set area = width * height %}
price + area * 0.5

The blocks {% if %}, {% elseif %}, {% else %}, {% set %} and {% for %} are allowed.

Important: how the price formula works

The price formula replaces the entire unit price – it is not a surcharge.

If the price calculation is active, the formula alone determines the price. Option surcharges are not added automatically – if you need them, include them via options.<identifier>.price in the formula.
If the price calculation is off, the rule is: product price + the sum of the selected option surcharges.

More about the interaction with cart and display under Price & cart.

Examples

Fixed surcharge

price + 15

Include an option's surcharge

price + options.material.price

Area price (width × height)

Dimensions from customer input in centimetres, price per square metre = €40:

price + (fields.width * fields.height / 10000) * 40

Quantity tiers (discount from a number of units)

{% if fields.quantity >= 100 %}
    price * 0.85
{% elseif fields.quantity >= 50 %}
    price * 0.9
{% else %}
    price
{% endif %}

Enforce a minimum price

max(price + options.accessory.price, 19.90)

Price per unit × quantity

(price + options.engraving.price) * fields.quantity|default(1)

Surcharge by material choice

{% if fields.material == 'oak' %}
    price + 80
{% elseif fields.material == 'walnut' %}
    price + 120
{% else %}
    price
{% endif %}

Round cleanly to two decimals

round(price + (fields.width * fields.height / 10000) * 40, 2)

Calculate a dimension (width formula)

Final width = base width + surcharge from input:

width + fields.extra_width|default(0)

Calculate weight (weight formula)

weight + options.material.weight

Generate a product number (text formula)

'SIGN-' ~ fields.colour ~ '-' ~ fields.width ~ 'x' ~ fields.height

Result e.g.: SIGN-gold-30x20

Show an interim result (result formula)

For a field of type Interim result:

'Area: ' ~ (fields.width * fields.height / 10000)|round(2) ~ ' m²'

Shows the customer live, e.g.: Area: 0.06 m²

Pre-fill a default value (default value formula)

width

Checking & error behaviour

Check the formula: While editing you can have a formula validated for correct syntax directly in the backend. Unknown variables or disallowed constructs are reported.
Robustness in the shop: If a formula does not produce a sensible result at runtime (e.g. due to a division by zero), the configurator automatically falls back to the base value (base price or base dimension). So your shop never shows an error, but in case of doubt the unchanged price.

Tips & pitfalls

Concatenate text with ~, calculate with + - * /. 'A' + 'B' does not work as expected.
Use the decimal point: 0.5, not 0,5.
Safeguard empty fields: fields.quantity|default(1) prevents calculating with an empty value.
Mind the units: convert lengths deliberately (e.g. cm → m² by dividing by 10000) so your square-metre price is correct.
abs, ceil, floor only as filters: value|ceil.
Start small: test a simple formula, check the result in the shop, then extend it step by step.