Noah was six hundred years old when the floodwaters came on the earth. And Noah and his sons and his wife and his sons’ wives entered the ark to escape the waters of the flood. Genesis 7:6-7

By the first day of the first month of Noah’s six hundred and first year, the water had dried up from the earth. Noah then removed the covering from the ark and saw that the surface of the ground was dry. By the twenty-seventh day of the second month the earth was completely dry.  Genesis 8:13-14

Approximately 1 year, 1 month and 27 days.  Noah was 600 years old when it started and 601 when it ended.

During that time...

• 40 days it rained
• 150 days the waters sat, flooding the earth
• 90 days the ark rested on the mountain
• 40 days later Noah opens the window to check to see if there is vegetation and dry land by sending a dove and raven out and waiting for them to return
• 7 days later he sends the dove out again and it does not return