For a self-employed individual, contributions are limited to 25% of your net earnings from self-employment (not including contributions for yourself), up to $61,000 for 2022 ($58,000 for 2021; $57,000 for 2020).

Here is an article on how much you can Contribution to a SEP plan.

1099 employee

Just to clarify, an employee gets a W-2.  Since you get a 1099, you are an independent contractor.