Bhishma’s age at the end of Mahabharat war
Bhishma’s Age could be approximately around 186.
Let us have a look into the events of Mahabaratha
After Bhishma was born, he was taken by Ganga to Devaloka and all the Education was given for 16 years.
After that, he learned archery and other warfare skills from Parasuram for 12 years. He was 28 years Old then.
After that he was handed over to Shantanu Maharaj by Ganga. Assume he live with him for 4 years. Now his age would be 32 years.
When he was 32, Shantanu married Satyavati. When Satyavati kids were born,when he was around 34.
Now Vichitravirya and his brother, spent their time in childhood for 16 years and there after they would have gone to learn warfare and other skills, which would have lasted for 12 years. So at this time Bhishma would be 34 + 28. 62 years.
That time chitrangadha would have died and within a year, Amba story happened. Bhimas Age 63.
From that time, in 2 years Ambika and Ambalika would have given birth to Dhirtirashtra and Pandu through sage Vyasa. Bhishma’s Age – 65 (At the time of Pandu’s Birth).
Similarly Pandu gone through his Childhood for 16 years and his education for 12 years. So when pandu was 28, Bhishma’s age would be 65 + 28. 93 years.
After Pandu’s education completed, he returned to Hastinapur and married Kunti and then Mathiri and his curse story would have happened.
He had gone to forests and approximately after 5 years (after completing education) Yudhistra would have born. Bhishma’s Age 98(At the time of Yudhistra’s Birth).
Pandu died when Yudhistra was 16 years. So Bhishma’s age 114 years.
Pandavas, after returning from forest, spent 6 months in Hastinapur and went for education in Drona’s Ashram for 12 years. So Bhisma’s age is 126.5 years
After returning to Hastinapur pandavas stayed for 6 months and went on a war with Drupada for an year. Bhishma Age – 128 years.
Yudhistra was crowned prince and stayed in Hastinapur for 5 years.
Entered and stayed in wax palace for 2 years.
Stayed in Ekachakrapuram for 6 months (slain of Bakasura) and married Draupadi.
At the time Draupadi marraige Bhishma’ Age – 135.5 years
Pandavas stayed in Panchala kingdom for an year after marriage, and returned to Hastinapur.
In Hastinapur they stayed for 5.5 years with Yudhistra as the prince. In this time Indraprastha was built.
Once Indraprastha built Pandava moved there. At that time Bhisma’s Age – 142 years
Arjuna went on pilgrimage for 12 years, since he had entered Yudhistra’s Room when he was with Draupadi, without their prior permission.
After Arjuna’s arrival Yudhistra ruled Indraprastha for another 16 years and performed Rajyasooga Yagna.
This happened for 2 years, and Yudhistra become Emperor.
At that time Bhishma’s Age – 142 + 12 + 16 + 2 – 172 years
Famous Dice Game began and Pandavas went to exile for 13 years. When they rerurned from exile Bhishma age – 185 years.
A year after they returned from exile, the Kurukshetra began.
Bhishma age – 186 at the time of war.