FTB-C000020 / Formula component

EMA Period-Label Equivalence

EMA period-label equivalence maps a conventional period label to its smoothing constant.

Also known asEMA span conversion

Advanced Formula defined 6 linked topicsPublished

Definitions

In plain terms

The period number attached to a conventional EMA is another way to describe its update speed: a larger period label corresponds to a smaller smoothing constant.

Technical

Under the conventional span mapping alpha = 2/(n+1), alpha 0.10 maps to n=19 and alpha 0.05 maps to n=39; the mapping does not choose the seed.

Scope

The period label is an equivalence convention for the update weight and must not be mistaken for a rolling window that discards all older data.

Formula

alpha = 2 / (n + 1)
LaTeX: \alpha = \frac{2}{n+1}
SymbolMeaningUnit
\alphaSmoothing constantdimensionless
nConventional EMA period labelobservations

Output unit: dimensionless

Examples

  • For n=19, alpha equals 2 divided by 20, or 0.10.

Common misconceptions

  • An EMA-19 still has influence from observations older than 19 periods.

Concept relationships

Prerequisites

Derived from

Required by

Where this concept is used

Tutorials planned

These catalogued topics use this concept, but their complete build has not shipped yet.

  • D04-F02-A01 Important
  • D04-F02-A02 Important
  • D04-F02-A03 Important
  • D04-F02-A05 Important
  • D04-F02-A06 Important
  • D07-F01-A02 Important

Evidence and governance

  1. Calculating the McClellan Oscillator McClellan Financial Publications · first party methodology

    Supports: preferred label, short definition, technical definition, formula, units

    Limits: Does not prescribe one universal initialization, missing-session, revision-resolution, rounding, or software interface policy.

  2. McClellan Oscillator StockCharts ChartSchool · secondary methodology

    Supports: technical definition, variant distinction

    Limits: Platform symbols, displayed thresholds, universe choices, and implementation details are vendor-specific rather than universal methodology requirements.

Reviewed by
Last reviewed
2026-07-26
Next review
2027-07-26
Record status
published
Written by

Fintech engineer building market-data and financial systems, and the author of every article, glossary record, and reference implementation on The Fintech Builder.