You would need to use your 2024 tax return to calculate the 2025 estimates. But I would just send in 20% of your estimated Net Profit to cover the self employment tax.
Self Employment tax (Scheduled SE) is automatically generated if a person has $400 or more of net profit from self-employment. You pay 15.3% SE tax on 92.35% of your Net Profit (If it is greater than $400). The 15.3% self employed SE Tax is to pay both the employer part and employee part of Social Security and Medicare (FICA). So you get social security credit for it when you retire.
The SE tax is already included in your tax due or reduced your refund. It is on the 1040 Schedule 2 line 4 which goes to 1040 line 23. The SE tax is in addition to your regular income tax on the net profit.
So for 1099 or self employment income you need to send in quarterly estimated payments or increase W2 withholding to cover the Self Employment tax.
here are the blank Estimates and instructions (the actual 1040ES forms are at the very bottom so scroll way down)
http://www.irs.gov/pub/irs-pdf/f1040es.pdf
Or you can pay directly on the IRS website https://www.irs.gov/payments
Be sure to pick the right kind of payment and year.....2025 Estimate
