# Function: vonBertalanffyMass()

[**lifecycle-kit**](https://jonbogaty.com/lifecycle-kit/api/readme/index.md)

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[lifecycle-kit](https://jonbogaty.com/lifecycle-kit/api/readme/index.md) / [bio-laws](https://jonbogaty.com/lifecycle-kit/api/bio-laws/readme/index.md) / vonBertalanffyMass


# Function: vonBertalanffyMass() {#function-vonbertalanffymass}


> **vonBertalanffyMass**(`age`, `maxMass`, `growthRate`, `t0?`, `b?`): `number`

Defined in: [bio-laws/lifeHistory.ts:36](https://github.com/jbcom/lifecycle-kit/blob/074e4e7b8038d3e2de9eb44c4b5b5aee0ef02b48/src/bio-laws/lifeHistory.ts#L36)

von Bertalanffy growth in mass.

Source: von Bertalanffy, L. (1938). "A quantitative theory of organic
growth." Human Biology, 10(2), 181-213.

  W(t) = W_max × (1 - e^(-K(t - t0)))^b

The standard model for indeterminate growers. Growth is fast while small
and asymptotes toward a maximum the organism never quite reaches — which is
why a well-fed creature does not grow without bound, and why the last
increment of size is the most expensive one it will ever buy.


## Parameters {#parameters}



### age {#age}


`number`


### maxMass {#maxmass}


`number`


### growthRate {#growthrate}


`number`


### t0? {#t0}


`number` = `0`


### b? {#b}


`number` = `3`


## Returns {#returns}


`number`