Reminder, an extension only extends the time to file, NOT the time to pay! If you think you will owe taxes, you should make a payment with extension to avoid incurring interest and penalties. 

DISCLAIMER: This is just general advice, not a personalized estimate. JenTaxPrep is NOT responsible for any penalties and interest that may accrue if this Rule of Thumb underestimates 

Rule of Thumb for Estimating Extension Payments

On the total of any 1099NEC/MISC or Self-employment income: 
20% to IRS 
5% to NY if you are an NYC resident
3% to applicable state if not an NYC resident (including other NY residents)
1% to applicable locality other than NYC (this is mostly for PA and OH residents, though there are a few other cities with income tax)
NOTE: If you did the recommended estimated payments already, you can skip this!
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On the total of any Capital Gains (profit from Stock Sales, Dividends, Crypto, etc) or any other income that doesn't have withholding (such as settlements, prizes, K1 income, some retirement income, W2 jobs that didn't withhold etc)
10% to IRS
5% to NY if you are an NYC resident
3% to applicable state if not an NYC resident (including other NY residents)

On the total of any Unemployment Income (as reported on your 1099G) 
10% to IRS if you did not have federal withholding
5% to NY if you are an NYC resident and had NY withholding or withholding from another state (excepting MD and WI) 
5% to NY if you are a non-NYC NY resident and did not have NY withholding or got unemployment from a state that doesn't tax it, such as CA, NJ, MD, PA or WI. 
8% to NY if you are an NYC resident and did not have any state withholding, or had MD/WI withholding. 
3% for residents of other states that do tax unemployment and have unemployment from a state that does not have state withholding (states with no income tax or AL, CA, MT, NJ, PA and VA do not tax UE) 

On the total of any W2 income earned in one of the no income tax states (so AK, FL, NH, NV, SD, TN, TX, WY or abroad/cruise ship)
5% to the state you live in if it has an income tax
3% additional to NY if you are an NYC resident

NYC residents who worked outside the city
3% to NY on any W2 that had taxes from another state

On the total of any Rental Income
5% to IRS
3% to NY if you are an NYC resident
2% to applicable state if not an NYC resident (including other NY residents)

IF YOU UNDERPAY WITH EXTENSION then you will accrue interest and penalties to both Federal and State, so when in doubt, overestimate and you will get it back when you file! Reminder, JenTaxPrep is not responsible for any interest and penalties that accrue due an underestimate of taxes.