Expression reference

What you can type

Expressions follow the usual order: brackets, then ^, then * and /, then + and -. Spaces don’t matter, and a decimal needs a point: 12.5, not 12,5.

A plain number takes the field’s unit: millimetres in a length, degrees in an angle. Counts, like the number of copies in a pattern, take plain numbers and round to the nearest whole one.

Type	To get
+ - * / ^ ()	Add, subtract, multiply, divide, power, group
mm cm m in	Lengths: 1 in is 25.4 mm
deg (or °) rad	Angles: (pi / 4) rad is 45°
pi (or π)	3.14159…
sqrt(x)	Square root: sqrt(30^2 + 40^2) is 50
sin(a) cos(a) tan(a)	Trigonometry, with a in degrees: sin(30) is 0.5
asin(x) acos(x) atan(x)	The angle back, in degrees: atan(1) is 45°
min(a, b, …) max(a, b, …)	The smallest or largest of any number of values
abs(x) round(x) floor(x) ceil(x)	Drop the sign, round to nearest, round down, round up

Units mix freely: 1 in + 2 mm is 27.4 mm.

When a field turns red

If Fillet can’t work out what you typed, the field turns red and says why underneath. The design keeps the last value that worked, and if you leave the field while it’s red, that value comes back.

Message	What to do
Unknown parameter ‘widht’	Check the spelling, or add the parameter first.
Function ‘sqrt’ needs parentheses	A function takes brackets: sqrt(2).
Missing ‘)’	Close every bracket you open.
Missing operator between numbers	Put +, -, * or / between them: 2 * 3, not 2 3.
Unknown unit ‘ft’	Use mm, cm, m or in for lengths, deg or rad for angles.
Expected a length, got angle	This field wants millimetres. Drop the angle unit.
Expected a plain number, got length	Counts take no unit. Use a parameter without one.
Cannot combine length and angle with ‘+’	Add lengths to lengths and angles to angles.
Circular reference: a → b → a	Two parameters use each other. Give one of them a value of its own.

Use parameters and expressionsName a size once and use it in every step.