IRS Tax Withholding Estimator for Self Employed

I’m waiting on my tax return from my CPA and have a bad feeling that even though I overpaid on my estimated taxes this year, it may not have been enough because of an income increase.

I’m fully self employed, but came across the IRS tax Withholding Estimator tool. It says it’s designed for those with w-2 income, but it has a section for self employment income and let me proceed with getting a withholding estimate despite not entering any W-2 income.

My question is, is this calculator missing any elements that would need to be considered to get an accurate estimate for someone who only has self employment income? Like does it take self employment tax into consideration as well as income tax?

Any advice would be helpful.