It really depends on your entire situation ... but a rule of thumb is 20% of gross income or 30% of net profits. 

What are estimated taxes?

https://ttlc.intuit.com/replies/3301588

Do I need to make estimated tax payments to the IRS?

https://ttlc.intuit.com/replies/3301891

Why did 1040-ES estimated tax vouchers print out? Do I need them?

https://ttlc.intuit.com/replies/3301872

How does TurboTax calculate my estimated tax payments?

https://ttlc.intuit.com/replies/3301730