According to the IRS "Many different factors can affect the timing of your refund after we receive your return. Even though we issue most refunds in less than 21 days, it’s possible your refund may take longer. Also, remember to take into consideration the time it takes for your financial institution to post the refund to your account."
As soon as 24 hours after the IRS has accepted your return you can check the status of your return by going to Where’s My Refund?