> ## Documentation Index
> Fetch the complete documentation index at: https://mehen.ophi.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# NPM — Number of Public Methods

> Number of public methods declared on classes and interfaces.

**NPM** (Number of Public Methods) counts the public methods exposed by classes and interfaces in a
file. NPM is the size of the unit's API surface.

## What mehen emits

| Key                      | Type  | Description                                         |
| ------------------------ | ----- | --------------------------------------------------- |
| `npm`                    | int   | Total public methods across classes and interfaces. |
| `npm.classes`            | int   | NPM contributed by classes.                         |
| `npm.interfaces`         | int   | NPM contributed by interfaces.                      |
| `npm.class_methods`      | int   | Alias of `npm.classes`.                             |
| `npm.interface_methods`  | int   | Alias of `npm.interfaces`.                          |
| `npm.classes_average`    | float | Mean public methods per class.                      |
| `npm.interfaces_average` | float | Mean public methods per interface.                  |
| `npm.total_methods`      | int   | Alias of `npm`.                                     |
| `npm.average`            | float | Mean public methods per declaration.                |

<Note>
  Despite the name, this metric has nothing to do with the npm package manager. NPM here stands for
  *Number of Public Methods*, a classic CK-style object-oriented metric.
</Note>

## What counts as "public"

| Language        | Public method is…                                            |
| --------------- | ------------------------------------------------------------ |
| Java / Kotlin   | A method declared `public` (or with no modifier in Kotlin).  |
| TypeScript / JS | A class method without `private` / `protected` / `#` prefix. |
| Python          | A method that does not start with `_`.                       |
| Ruby            | A method *not* declared `private` or `protected`.            |

## How to read it

Conventional reading:

| `npm` | Interpretation            |
| ----- | ------------------------- |
| 1–10  | Small, focused class.     |
| 11–25 | Normal application class. |
| 26+   | God-class candidate.      |

Pair with [WMC](/metrics/code/wmc) to gauge whether the surface is wide *and* heavy, and with
[NPA](/metrics/code/npa) to gauge whether the class encapsulates state.

## References

* Lorenz, M. & Kidd, J. (1994). *Object-Oriented Software Metrics: A Practical Guide.* Prentice Hall.
* Chidamber & Kemerer (1994). *A Metrics Suite for Object Oriented Design.* IEEE TSE.

## See also

* [NPA](/metrics/code/npa) — number of public attributes.
* [NOM](/metrics/code/nom) — total methods (public + private).
* [WMC](/metrics/code/wmc) — weighted methods per class.