I-526: 20 to 26 months
I-829: 29 to 37.5 months
View processing times here
If you have been a Permanent Resident for at least 5 years and during that five years, you have not been outside the United States for 30 months or more, you may be eligible for U.S. citizenship or simply maintain your Permanent Residence, renewing it every 10 years.
To gain citizenship, begin by submitting the appropriate forms to the United States Citizenship and Immigration Services. For more on becoming a citizen visit the USCIS website!