Calculated Field
A read-only field whose value is derived from a formula using other field values.
Overview
The Calculated Field automatically computes a value from a formula expression you define. The formula can reference other field values using their name property and supports standard arithmetic operators, comparison operators, and a set of built-in functions.
The field updates in real time as the referenced fields change. It is displayed as a read-only input. The computed value is included in the submission data like any other field.
Note: Calculated fields are evaluated client-side in the browser. Do not rely on them for server-side business logic or security-critical computations.
Properties
| Property | Type | Default | Description |
|---|---|---|---|
| id | string | — | Unique field identifier (UUID in the builder). |
| type | string | calculated | Must be "calculated". |
| label | string | — | Human-readable label shown above the field or step heading. |
| instruction | string | undefined | Optional help text below the label. |
| formula | string | "" | Expression with {field_id} tokens, e.g. "{qty}*{price}". |
| conditionalRules | array | undefined | Show this field when any rule matches another field's value. |
| logic | object | undefined | Simple visibility: depends_on + show_if_value. |
Formula Syntax
Reference any other field by wrapping its name in curly braces: {field_name}. Standard math operators apply: + - * / ( ).
// Total price
{quantity} * {unit_price}
// Tax-inclusive price
{subtotal} * 1.13
// Conditional logic
IF({quantity} > 10, {unit_price} * 0.9, {unit_price})
// String concatenation
CONCAT({first_name}, " ", {last_name})JSON Schema
{
"type": "calculated",
"label": "Total Amount",
"name": "total_amount",
"formula": "{quantity} * {unit_price} * (1 + {tax_rate} / 100)",
"format": "currency",
"currency": "USD",
"decimalPlaces": 2
}Common Use Cases
- Order totals: quantity × unit price with tax or shipping rolled in
- Quote builders surfacing subtotals before respondents submit
- BMI-style health calculators from height and weight inputs
- Concatenating first and last names for a read-only display label
- Previewing derived values during data entry while server logic still re-verifies totals