I need some help calculating how much tax I owe after selling stock. Can you help me calculate how much estimated tax I need to pay and by when?

See this for calculating 2020 estimated taxes - https://ttlc.intuit.com/community/tax-payments/help/can-turbotax-calculate-next-year-s-federal-estim...

See this for paying estimated taxes - https://ttlc.intuit.com/community/tax-payments/help/how-do-i-make-estimated-tax-payments/00/25875

You can calculate your 2020 estimated taxes and generate the payment vouchers by doing this:

1. With your tax return open, search for 1040-es (be sure to include the dash) and select the Jump to link.
2. Answer No to the question Do you want to change your W-4 withholdings for 2020?
3. Answer the questions about things like your 2020 filing status, income, and deductions.
4. Eventually, you'll come to the Print Vouchers? screen. Answer Yes and we'll include your 2020 1040-ES payment vouchers when you print a copy of your return later.

After you file ... to open the account ... log in and scroll down and click on ADD A STATE.