How to do Maths

Last updated March 23, 2026

Liquid has no math operators like +, -, *, or /. Instead, all arithmetic is done through filters — you pipe a value through a filter to transform it. This page teaches common calculation patterns you’ll need when building templates.

Basic arithmetic

The four core arithmetic filters are plus, minus, times, and divided_by. Each takes a value on the left and a parameter on the right:

{{ 10 | plus: 5 }}        -> 15
{{ 10 | minus: 3 }}       -> 7
{{ 10 | times: 4 }}       -> 40
{{ 10 | divided_by: 3 }}  -> 3

Practical examples

Calculating a line item total from your data:

{{ item.quantity | times: item.unit_price }}

Applying a 10% discount:

{% assign discounted = subtotal | times: 0.9 %}
{{ discounted }}

Adding 20% VAT to a subtotal:

{{ subtotal | times: 1.20 }}

Rounding

Three filters control decimal precision:

{{ 4.6 | round }}     -> 5
{{ 4.3 | round }}     -> 4
{{ 4.123 | round: 2 }} -> 4.12

{{ 4.1 | ceil }}      -> 5
{{ 4.1 | floor }}     -> 4

Integer division truncates

When divided_by receives an integer divisor, it returns a truncated integer — not a rounded result:

{{ 5 | divided_by: 3 }}    -> 1  (not 1.67)
{{ 5 | divided_by: 3.0 }}  -> 1.6666666666666667

Use a decimal divisor (like 3.0) if you need a precise result.

Chaining calculations

Filters can be chained left to right. Each filter receives the output of the previous one:

{{ price | times: quantity | times: 1.20 | round: 2 }}

This multiplies price by quantity, applies 20% VAT, and rounds to 2 decimal places — all in a single expression.

A complete invoice line example:

{% for item in lineItems %}
  <tr>
    <td>{{ item.product }}</td>
    <td>{{ item.quantity }}</td>
    <td>${{ item.price | with_delimiter, precision: 2 }}</td>
    <td>${{ item.price | times: item.quantity | with_delimiter, precision: 2 }}</td>
  </tr>
{% endfor %}

Formatting numbers

Liquid arithmetic filters return raw numbers. To display them nicely (thousand separators, fixed decimals, sprintf patterns), use the with_delimiter and format filters.

Further reading

  • Filters — complete reference for all built-in and PDFMonkey-specific filters

Frequently asked questions

How do I do math in Liquid templates?
Liquid has no math operators. Use filters instead: plus, minus, times, and divided_by. For example, {{ 10 | plus: 5 }} returns 15.
Why does divided_by return a wrong result in Liquid?
When the divisor is an integer, divided_by truncates the result to an integer. Use a decimal divisor (e.g., 3.0 instead of 3) to get a precise floating-point result.
How do I round numbers in a PDFMonkey template?
Use the round filter for standard rounding ({{ 4.6 | round }} returns 5), ceil to round up, or floor to round down. Pass a precision argument to control decimal places: {{ 4.123 | round: 2 }} returns 4.12.
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