---
title: promql.extrapolatedRate() function
description: >
  `promql.extrapolatedRate()` is a helper function that calculates extrapolated rates over
  counters and is used to implement PromQL's
  [`rate()`](https://prometheus.io/docs/prometheus/latest/querying/functions/#rate),
  [`delta()`](https://prometheus.io/docs/prometheus/latest/querying/functions/#increase),
  and [`increase()`](https://prometheus.io/docs/prometheus/latest/querying/functions/#delta) functions.
menu:
  flux_v0_ref:
    name: promql.extrapolatedRate
    parent: internal/promql
    identifier: internal/promql/extrapolatedRate
weight: 201
---

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`promql.extrapolatedRate()` is a helper function that calculates extrapolated rates over
counters and is used to implement PromQL's
[`rate()`](https://prometheus.io/docs/prometheus/latest/querying/functions/#rate),
[`delta()`](https://prometheus.io/docs/prometheus/latest/querying/functions/#increase),
and [`increase()`](https://prometheus.io/docs/prometheus/latest/querying/functions/#delta) functions.

**Important**: The `internal/promql` package is not meant for external use.

##### Function type signature

```js
(
    <-tables: stream[{A with _value: float, _time: time, _stop: time, _start: time}],
    ?isCounter: bool,
    ?isRate: bool,
) => stream[{B with _value: float}]
```

{{% caption %}}
For more information, see [Function type signatures](/flux/v0/function-type-signatures/).
{{% /caption %}}

## Parameters

### tables

Input data. Default is piped-forward data (`<-`).



### isCounter

Data represents a counter.



### isRate

Data represents a rate.