---
title: "Constant VUs | Grafana k6 documentation"
description: "A fixed number of VUs execute as many iterations as possible for a specified amount of time."
---

> For a curated documentation index, see [llms.txt](/llms.txt). For the complete documentation index, see [llms-full.txt](/llms-full.txt).

# Constant VUs

With the `constant-vus` executor, a fixed number of VUs execute as many iterations as possible for a specified amount of time.

For a shortcut to this executor, use the [VUs](/docs/k6/latest/using-k6/k6-options/reference/#vus) and [duration](/docs/k6/latest/using-k6/k6-options/reference/#duration) options.

## Options

Besides the [common configuration options](/docs/k6/latest/using-k6/scenarios/#options), this executor has the following options:

Expand table

| Option             | Type    | Description                                         | Default |
|--------------------|---------|-----------------------------------------------------|---------|
| duration(required) | string  | Total scenario duration (excluding `gracefulStop`). | \-      |
| vus                | integer | Number of VUs to run concurrently.                  | `1`     |

## When to use

Use this executor if you need a specific number of VUs to run for a certain amount of time.

## Example

This examples schedules 10 VUs to run constantly for a duration 30 seconds.

JavaScript ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy

```javascript
import http from 'k6/http';
import { sleep } from 'k6';

export const options = {
  discardResponseBodies: true,
  scenarios: {
    contacts: {
      executor: 'constant-vus',
      vus: 10,
      duration: '30s',
    },
  },
};

export default function () {
  http.get('https://test.k6.io/contacts.php');
  // Injecting sleep
  // Total iteration time is sleep + time to finish request.
  sleep(0.5);
}
```

## Observations

The following graph depicts the performance of the [example](#example) script:

Based upon our test scenario inputs and results:

- The number of VUs is fixed at 10, and are initialized before the test begins;
- Overall test duration is fixed at the configured 30 second duration;
- Each *iteration* of the `default` function is expected to be roughly 515ms, or ~2/s;
- Maximum throughput (highest efficiency) is therefore expected to be ~20 iters/s, `2 iters/s * 10 VUs`;
- We see that the maximum throughput is reached and maintained for the majority of the test;
- Approximately 600 iterations are therefore performed in total, `30 seconds * 20 iters/s`.