---
title: "Time Of Concentration Calculator"
canonical: "https://help.innovyze.com/space/infodrainage2021v1/16547869/Time%20Of%20Concentration%20Calculator"
format: markdown
---
The **Time Of Concentration Calculator** allows the [Time of Concentration](https://help-innovyze.atlassian.net/wiki/spaces/infodrainage2021v1/pages/16547874) to be calculated for the [Runoff Generation](https://help-innovyze.atlassian.net/wiki/spaces/infodrainage2021v1/pages/16547908).

![image](media://0b6db5ac-d2bb-44e1-a1af-ef5d04bcec7f)


You can select various methods to calculate the amount of time. Click the following links for more information about these methods:

> ⚠️ Some of the methods may not be available for your region. For more information, refer to the [Regionalisation](https://help-innovyze.atlassian.net/wiki/spaces/infodrainage2021v1/pages/16548015) topic.

- [Friend's Equation](https://help-innovyze.atlassian.net/wiki/spaces/infodrainage2021v1/pages/16547855)
- [Alameda Method](https://help-innovyze.atlassian.net/wiki/spaces/infodrainage2021v1/pages/16547884)
- [Bransby Williams Method](https://help-innovyze.atlassian.net/wiki/spaces/infodrainage2021v1/pages/16547882)
- [Izzard's Formula](https://help-innovyze.atlassian.net/wiki/spaces/infodrainage2021v1/pages/16547888)
- [Kerby's Equation](https://help-innovyze.atlassian.net/wiki/spaces/infodrainage2021v1/pages/16547886)
- [Kinematic Wave](https://help-innovyze.atlassian.net/wiki/spaces/infodrainage2021v1/pages/16547853)
- [Kirpich's Equation](https://help-innovyze.atlassian.net/wiki/spaces/infodrainage2021v1/pages/16547859)
- [US Federal Aviation Authority](https://help-innovyze.atlassian.net/wiki/spaces/infodrainage2021v1/pages/16547857)
- [TR-55 Methods](https://help-innovyze.atlassian.net/wiki/spaces/infodrainage2021v1/pages/16547880)

Some initial values on the calculator are populated based on the current Inflow:

- **Area** - Based on the current inflow's Area.
- **Catchment Slope** - Maximum slope derived from the Outline if a surface file is available. If no surface file is used, defaults to 1:200.
- **Catchment Length** - The maximum distance between any two points on the outline of the area.
- **Runoff Coefficient** - The Preliminary or Runoff Coefficient, depending on where the calculator is launched from. Defaults to 0 if it is not specified.

All of these values can be overwritten in the Calculator without affecting the values on the Inflow.