Armhole Binding Stretch Factor Tool

Description

Return opening/relaxedBinding and that factor minus one.

Ease, gathering and stretch compare lengths on a chosen baseline. Extra-length ratio, finished/flat ratio and extension from relaxed length are different conventions, so the denominator must be explicit.

Return opening/relaxedBinding and that factor minus one.

When to use this tool

Use Armhole Binding Stretch Factor when you need one stated ease, gauge or stretch relationship.

How to use the tool and how it works

Enter opening, relaxedBinding. Use the units and conventions below.
Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
Read extensionFraction, installedFactor. Use the output convention below.

Require positive opening and relaxed binding lengths. Return opening/relaxedBinding and that factor minus one.^[1]

Input field	Meaning and units	Accepted input
opening	Opening	Required. Finite number; strictly above 0.
relaxedBinding	Relaxed Binding	Required. Finite number; strictly above 0.

Output field	Interpretation	Returned shape
extensionFraction	Extension Fraction	Required. Finite number.
installedFactor	Installed Factor	Required. Finite number.

json

{
  "input": {
    "opening": 50,
    "relaxedBinding": 40
  },
  "output": {
    "extensionFraction": 0.25,
    "installedFactor": 1.25
  }
}

Limitations and assumptions

Extension can be negative. The result does not establish a safe stretch limit, recovery, suitable binding material or garment fit.
Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.

Alternative or Complementary methods

Test the intended material and review the complete pattern fit. Account for recovery, shrinkage, directional stretch and construction instead of interpreting a length ratio as guaranteed comfort or suitability.

References

Calculation and input contract: fashion/armhole-binding-stretch-factor — tool.io

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