You'll typically receive your Federal refund within 21 days of e-filing your return.
Mailed returns typically take 4 weeks longer to be processed. It takes that amount of time for your return to show up in their system, sometimes a bit longer if they are backed up.
You can track both your Federal and State refunds here.:
There are quite a number items that determine how much you receive in tax refunds. Some major ones include:
For more info, check out this article about understanding your tax refund.