How do I compute estimated states taxes for the state of lndiana

The simplest way to go about it is to take your 2024 state liability (line 11 on IN IT-40), multiply it by 110% (depending on your income, you could do 100% instead of 110%, but this way, you'd approach it more conservatively). Once you arrive at a number, reduce it by the estimated amount of withholdings by your employer (if any). The remaining amount is divided by 4 and paid quarterly. 

Indiana estimated tax due dates are the same as federal: April 15, June 15, September 15, and January 15 (next year). 

Here is an example:

Let's say your IT-40, line 11 for 2024, shows $2,000. Multiplying it by 110% results in $2,200. Let's assume that your employer will withhold $1,500 in IN taxes. That leaves you with $700 of unpaid taxes. That's $175 each quarter. 

This doesn't guarantee that you won't owe when you prepare your taxes. But it will cover the minimum under safe harbor, and you will not incur penalties for late payment. As long as you pay the rest by the due date of the return.