Variables & Formulas

Variables are a powerful feature that allow you to create dynamic, parametric patterns. Instead of using fixed measurements, you can define named values that can be reused throughout your pattern and automatically update when changed.

Understanding the Concepts

Variables

A variable is a named value that you can reference throughout your pattern. Variables store a single numeric value (like 42 or 2.5) and can be used in place of any measurement.

Example: Create a variable called SeamAllowance with value 1 (cm), then use it for all seam allowances in your pattern.

Formulas

A formula is a mathematical expression that calculates a variable's value based on other variables or expressions. When the inputs change, the formula automatically recalculates.

Example: Create a formula BagWidth / 2 + 2 that automatically updates when you change BagWidth.

Expressions

Expressions are special functions and references that let you access pattern geometry like point positions, line lengths, and panel dimensions. They can be used inside formulas.

Example: Use A1.A2 to get the length of a line, or A.width to get a panel's width.

Creating Variables

Simple Variables (Fixed Value)

Open the Variables section in the right sidebar
Click the + button to add a new variable
Enter a name (e.g., SeamAllowance)
Enter a value (e.g., 1.5)
Press Enter or click the checkmark

Formula Variables (Calculated Value)

Click the + button to add a new variable
Enter a name (e.g., HalfWidth)
Click the ƒx button to switch to formula mode
Enter your formula (e.g., BagWidth / 2)
Press Enter or click the checkmark

The formula editor shows a preview of the calculated value in yellow.

Expression Reference

These expressions can be inserted using the code button in the formula editor.

Panel Properties

Access overall panel dimensions:

Expression	Description
`A.width`	Width of panel A
`A.height`	Height of panel A
`A.perimeter`	Total perimeter of panel A
`A.area`	Area of panel A (in square units)
`A.pointCount`	Number of points in panel A

Point Expressions

Access point positions and line measurements:

Expression	Description
`A1`	Point reference (for use in functions)
`A1.x`	X coordinate of point 1 on panel A
`A1.y`	Y coordinate of point 1 on panel A

Line Properties

Access line measurements between two points:

Expression	Description
`A1.A2`	Distance between point 1 and point 2 (shorthand for `.length`)
`A1.A2.length`	Length of line from A1 to A2
`A1.A2.angle`	Angle of line A1-A2 in degrees
`A1.A2.curve`	Curve amount of line A1-A2
`A1.A2.seam`	Seam allowance for line A1-A2

Measurement Functions

Expression	Description
`dist(A1, A2)`	Distance between two points
`angle(A1, A2)`	Angle of line in degrees
`curve(A1, A2)`	Curve amount of the line

Construction

Expression	Description
`seam()`	Global seam allowance value
`A.seam`	Panel A's seam allowance (0 if disabled)

Math Functions

Function	Description
`min(a, b)`	Minimum of two values
`max(a, b)`	Maximum of two values
`abs(x)`	Absolute value
`round(x)`	Round to nearest integer
`floor(x)`	Round down
`ceil(x)`	Round up
`sqrt(x)`	Square root
`pow(x, n)`	Power (x to the n)
`avg(a, b)`	Average of two values
`mod(a, b)`	Modulus (remainder)
`sin(x)`	Sine (x in radians)
`cos(x)`	Cosine (x in radians)
`tan(x)`	Tangent (x in radians)

Conditional Expressions

Use ternary expressions to create values that change based on conditions:

Expression	Description
`x > y ? a : b`	If x greater than y, use a; otherwise b
`x >= y ? a : b`	If x greater than or equal to y, use a; otherwise b
`x == y ? a : b`	If x equals y, use a; otherwise b
`x != y ? a : b`	If x not equal to y, use a; otherwise b

Examples:

Name	Formula	Description
Margin	`BagWidth > 30 ? 5 : 3`	Wider margin for large bags
StrapWidth	`BagHeight > 50 ? 5 : BagHeight > 30 ? 3.5 : 2.5`	Chained: 3 sizes based on height

Nesting Conditionals

You can nest ternary expressions or combine them with other formulas: base + (margin > 5 ? 16 : 8)

Practical Examples

Example 1: Parametric Backpack

Create a backpack with variables for key dimensions:

Variables (fixed values):

Name	Value
BagHeight	45
BagWidth	30
BagDepth	15
SeamAllowance	1

Formulas (calculated):

Name	Formula
HalfWidth	`BagWidth / 2`
FrontPanelWidth	`BagWidth + BagDepth`
StrapLength	`BagHeight * 2 + 20`
PocketWidth	`BagWidth - 4`

Now when you change BagWidth, all related measurements update automatically!

Example 2: Dynamic Seam Allowance

Link seam allowance to panel dimensions:

Name	Formula
CutWidth	`A.width + SeamAllowance * 2`
CutHeight	`A.height + SeamAllowance * 2`

Example 3: Matching Panel Dimensions

Ensure the bag bottom matches the front panel width:

Name	Formula
BottomWidth	`A.width`

This makes the bottom panel always match the front panel's width.

Example 4: Calculate Fabric Requirements

Name	Formula
TotalArea	`A.area + B.area + C.area`
FabricLength	`round(TotalArea / FabricWidth)`

Example 5: Proportional Pocket Sizing

Create pocket dimensions based on the main bag:

Name	Formula
PocketWidth	`BagWidth * 0.8`
PocketHeight	`BagHeight * 0.4`
ZipperLength	`PocketWidth - 2`

Example 6: Using Point Positions

Calculate the center point of a panel edge:

Name	Formula
CenterX	`(A1.x + A2.x) / 2`
CenterY	`(A1.y + A2.y) / 2`

Example 7: Strap Calculations

Calculate strap dimensions with min/max bounds:

Name	Formula	Description
StrapLength	`max(80, BagHeight * 2.5)`	At least 80cm, scales with bag
StrapWidth	`min(5, max(2.5, BagHeight * 0.1))`	Between 2.5 and 5cm

Example 8: Roll-Top Calculations

Name	Formula
RollPanelHeight	`RollHeight + 5`
BuckleSpacing	`BagWidth / 3`

Example 9: Line Length Reference

Reference actual line lengths from your pattern:

Name	Formula	Description
SideLength	`A1.A2`	Length of line from point 1 to 2
Diagonal	`dist(A1, A3)`	Distance between any two points
TotalEdge	`A1.A2 + A2.A3 + A3.A4`	Sum of multiple lines

You can also link variables directly from the canvas using the Quick Edit popup. Double-click on any point or line to open it, then use the link icon to connect fields to variables—or create new variables on the spot.

See Point Editing → Quick Edit Popup for full details.

Linking Variables to Inputs

Variables can be linked to any numeric input in the pattern editor:

Click on any numeric input field (e.g., point X position, line length)
Click the link icon that appears
Select a variable from the dropdown
The input now displays the variable name and updates automatically

Linked inputs show:

Variable name when not hovering
Current value when hovering

note

When a point coordinate is linked to a variable, you cannot drag that point in that direction (X or Y). Keyboard arrow keys are also blocked for the linked direction.

Variable Modes

Variable modes let you save and switch between different configurations of your variables — like sizes (Small, Medium, Large) or product variants. Switching a mode instantly updates all variable values and the entire pattern.

Creating Modes

Click the Proportions icon () in the Variables section toolbar
This creates two modes: Default (your current values) and Mode 2 (a copy)
Click the + button to add more modes

Switching Modes

Click any mode tab to switch. All non-formula variable values update instantly, and formula variables recalculate from the new values.

Managing Modes

Rename: Double-click a mode tab to edit its name
Delete: Click the × on the active tab, or right-click any tab and select Delete
Diff highlighting: When viewing a non-default mode, values that differ from the Default mode are shown in blue

Mode Switcher in Variable Graph

When modes exist, a dropdown pill appears in the Variable Graph toolbar showing the active mode. Click it to switch modes from the graph view.

How Modes Work

Each mode stores a snapshot of non-formula variable values
Formula variables use the same formula across all modes — they recalculate based on the mode's input values
Adding a new variable while modes exist uses the variable's default value; other modes pick it up on switch
Deleting the second-to-last mode removes all modes, returning to normal behavior

Variable Groups

Organize your variables into groups for better management:

Click the folder+ icon to create a new group
Drag variables into groups
Collapse/expand groups by clicking the folder icon

Tip: Create groups like "Dimensions", "Pockets", "Straps", "Hardware" to keep variables organized.

Tips & Best Practices

Smart Naming

Click the wand icon inside the name input to auto-generate a name based on the variable's content:

Formula variables: Uses the expression as the name (e.g., A1.A2 or A.width+SeamAllowance*2)
Conditional formulas: Names like bool_margin based on the variables used
Slider variables: Named range1, range2, etc.
Value variables: Uses the value as the name, or var1, var2, etc.

Naming Conventions

Use descriptive names: BagWidth not BW
Use CamelCase or underscores: seam_allowance or SeamAllowance
Avoid spaces and special characters

Formula Organization

Break complex calculations into multiple variables
Use intermediate variables for clarity:

HalfWidth = BagWidth / 2

PocketWidth = HalfWidth - 2

ZipperLength = PocketWidth - 1

Unit Awareness

Variables automatically convert when switching between cm and inches
Expressions like A1.x return values in the current display unit
Keep this in mind when creating formulas with fixed values

Performance

Formula variables recalculate when their dependencies change
Avoid creating circular dependencies (A depends on B, B depends on A)
For patterns with many variables, consider grouping related calculations

Troubleshooting

Formula shows "—" (invalid)

Check for typos in variable names
Ensure referenced variables exist
Verify expression syntax (e.g., A1.x not A1x)

Variable not updating

Make sure dependent variables are formula-based
Check that the formula references the correct variable name
Verify the shape/point being referenced exists

Duplicate name error

Variable names must be unique (case-insensitive)
The name input shows a red border when duplicate detected

Value seems wrong after unit change

Expressions automatically convert to display units
Fixed values in formulas stay as-is (they're unitless numbers)
If mixing, ensure consistent unit expectations

Understanding the Concepts​

Variables​

Formulas​

Expressions​

Creating Variables​

Simple Variables (Fixed Value)​

Formula Variables (Calculated Value)​

Expression Reference​

Panel Properties​

Point Expressions​

Line Properties​

Measurement Functions​

Construction​

Math Functions​

Conditional Expressions​

Practical Examples​

Example 1: Parametric Backpack​

Example 2: Dynamic Seam Allowance​

Example 3: Matching Panel Dimensions​

Example 4: Calculate Fabric Requirements​

Example 5: Proportional Pocket Sizing​

Example 6: Using Point Positions​

Example 7: Strap Calculations​

Example 8: Roll-Top Calculations​

Example 9: Line Length Reference​

Quick Edit Popup​

Linking Variables to Inputs​

Variable Modes​

Creating Modes​

Switching Modes​

Managing Modes​

Mode Switcher in Variable Graph​

How Modes Work​

Variable Groups​

Tips & Best Practices​

Smart Naming​

Naming Conventions​

Formula Organization​

Unit Awareness​

Performance​

Troubleshooting​

Formula shows "—" (invalid)​

Variable not updating​

Duplicate name error​

Value seems wrong after unit change​