# Swap

SpiritSwap provides users a simple way to swap tokens on Fantom via automated liquidity pools. In a swap, one token is sold to buy another token. The rate of the swap is determined by the AMM with the equation:

$$
x\*y=k
$$

Where *x* = the number of $AAA tokens, *y* = the number of $BBB tokens, and *k* is a constant. The trader is charged a 0.3% fee to make a swap.

![Figure 1. Example of a swap on SpiritSwap.](https://1831120487-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MXVLUYT4_8bBeXXW_1r%2F-MYhT7SU6mYCkSO7vIeb%2F-MYhUonFaB0aeHGqs_Rp%2Fimage.png?alt=media\&token=0ce16bdb-aeb2-458e-9fd6-763d9cfc08ae)

In Figure 1, a trader is swapping $AAA token for $BBB tokens. The trader sends 100 $AAA tokens to the AMM. A 0.3% fee is applied and 0.3 $AAA tokens are not included in the swap. The remaining 99.7 $AAA tokens are swapped in the AMM to $BBB tokens. Since the AMM will be losing $BBB tokens, it must gain $AAA tokens to keep *k* constant. The equation:

$$
(1,000+99.7)\*(10-y)=10,000
$$

Can be solved for *y* to give the number of $BBB tokens that the trader will receive. The 0.3% fee of 0.3 $AAA tokens are directly added to the liquidity pool reserves, slightly increasing the value of *k.*