The Bible doesn’t reveal an exact age of Jacob for when he married, but we can get a good estimate.

We know that Joseph was 30 years old when Pharaoh set him over all of Egypt, and that the seven years of plenty happened shortly afterwards.

Gen 41:46  Joseph was thirty years old when he stood before Pharaoh king of Egypt. And Joseph went out from the presence of Pharaoh, and went throughout all the land of Egypt.
Gen 41:47  Now in the seven plentiful years the ground brought forth abundantly.

Gen 41:32  And the dream was repeated to Pharaoh twice because the thing is established by God, and God will shortly bring it to pass.

So, Joseph was 37 at the start of the 7 years of famine.

It was two years into the famine when Joseph revealed his identity to his brothers and implored his brothers to bring their father to Egypt.

Gen 45:6  For these two years the famine has been in the land, and there are still five years in which there will be neither plowing nor harvesting.
Gen 45:7  And God sent me before you to preserve a posterity for you in the earth, and to save your lives by a great deliverance.
Gen 45:8  So now it was not you who sent me here, but God; and He has made me a father to Pharaoh, and lord of all his house, and a ruler throughout all the land of Egypt.
Gen 45:9  “Hurry and go up to my father, and say to him, ‘Thus says your son Joseph: “God has made me lord of all Egypt; come down to me, do not tarry.

So, Joseph was about 39 years old when his father, Jacob, arrived in Egypt.

Jacob lived 17 years in Egypt and died when he was 147 years old.

Gen 47:28  And Jacob lived in the land of Egypt seventeen years. So the length of Jacob’s life was one hundred and forty-seven years.

So, Joseph was about 56 years old (39 + 17) when his father Jacob died (aged 147).  And so, Jacob was about 91 years old (147 – 56) when Joseph was born.

Looking at Jacob’s life, he worked for his uncle, Laban, for 20 years.  When Jacob left Laban, he reminded his uncle of the length of his service.

Gen 31:38  These twenty years I have been with you; your ewes and your female goats have not miscarried their young, and I have not eaten the rams of your flock.

But Jacob did not marry Rachel and Leah until he had worked 7 years.

Gen 29:20  So Jacob served seven years for Rachel, and they seemed only a few days to him because of the love he had for her.

So, Jacob married and started having children 7 years into his 20 years of service to Laban.  Jacob’s wife, Leah, had four sons in quick succession, and then stopped bearing.

Gen 29:31  When the LORD saw that Leah was unloved, He opened her womb; but Rachel was barren.
Gen 29:32  So Leah conceived and bore a son, and she called his name Reuben; for she said, “The LORD has surely looked on my affliction. Now therefore, my husband will love me.”
Gen 29:33  Then she conceived again and bore a son, and said, “Because the LORD has heard that I am unloved, He has therefore given me this son also.” And she called his name Simeon.
Gen 29:34  She conceived again and bore a son, and said, “Now this time my husband will become attached to me, because I have borne him three sons.” Therefore his name was called Levi.
Gen 29:35  And she conceived again and bore a son, and said, “Now I will praise the LORD.” Therefore she called his name Judah. Then she stopped bearing.

At this point Jacob was at least 4 years into his marriage.  Then the hand maidens of Rachel and Leah (Bilhah and Zilpah) each bore two sons, whose pregnancies may have overlapped.

Gen 30:5  And Bilhah conceived and bore Jacob a son.
Gen 30:6  Then Rachel said, “God has judged my case; and He has also heard my voice and given me a son.” Therefore she called his name Dan.
Gen 30:7  And Rachel’s maid Bilhah conceived again and bore Jacob a second son.
Gen 30:8  Then Rachel said, “With great wrestlings I have wrestled with my sister, and indeed I have prevailed.” So she called his name Naphtali.
Gen 30:9  When Leah saw that she had stopped bearing, she took Zilpah her maid and gave her to Jacob as wife.
Gen 30:10  And Leah’s maid Zilpah bore Jacob a son.
Gen 30:11  Then Leah said, “A troop comes!” So she called his name Gad.
Gen 30:12  And Leah’s maid Zilpah bore Jacob a second son.
Gen 30:13  Then Leah said, “I am happy, for the daughters will call me blessed.” So she called his name Asher.

At this point Jacob was at least 6 years into his marriage.  Leah then had two more sons and a daughter.

Gen 30:17  And God listened to Leah, and she conceived and bore Jacob a fifth son.
Gen 30:18  Leah said, “God has given me my wages, because I have given my maid to my husband.” So she called his name Issachar.
Gen 30:19  Then Leah conceived again and bore Jacob a sixth son.
Gen 30:20  And Leah said, “God has endowed me with a good endowment; now my husband will dwell with me, because I have borne him six sons.” So she called his name Zebulun.
Gen 30:21  Afterward she bore a daughter, and called her name Dinah.

At this point Jacob was at least 9 years into his marriage.  Rachel then had Joseph.

Gen 30:22  Then God remembered Rachel, and God listened to her and opened her womb.
Gen 30:23  And she conceived and bore a son, and said, “God has taken away my reproach.”
Gen 30:24  So she called his name Joseph, and said, “The LORD shall add to me another son.

When Joseph was born, Jacob was at least 10 years into his marriage.  Since Joseph was born before Jacob and all his family left Laban 13 years into his marriage (after 20 years of service, Gen 31:38), Joseph was born no later than 13 years into Jacob’s marriage.

We established earlier that Jacob was about 91 years old when Joseph was born.  Since Joseph was born 10 to 13 years into Jacob’s marriage, Jacob must have married when he was about 78 to 81 years old. 

Thus, Jacob was about 80 years old when he married.