Usually pending can last any where from one day to three weeks. If it hasn't been three weeks then not to worry your return will be processed.
Please refer to the following help article for the details on your pending status.
What does pending mean?
If it has been longer than 21 days and your return is still processing, please contact the IRS directly.
Look at the IRS contact information below.
What if my IRS refund is taking longer than 21 days?