What is the age of Arjuna at the time of Mahabharata war?

Sage Vyasa did not provide the ages of either Pandavas or Kauravas clearly.

However, it was mentioned that Pandavas born with a gap of 1 year each. 

In Southern recension, it was mentioned that at the death of Pandu, the age of Arjuna was 14, but BORI did not mention it.

The only information that is available is

a) at his death Drona was described to be at the age of 85 years and even BORI included this aspect.

आकर्णपलितः श्यामो वयसाशीतिकात्परः ।

रणे पर्यचरद्द्रोणो वृद्धः षोडशवर्षवत् ॥

b) Abhimanyu was described to be in adolescence age - may be 16–18 years of age, at the time of his death. At his death, it was narrated that he did not reach his adulthood.

अभिमन्यौ हते राजञ्शिशुकेऽप्राप्तयौवने ।

सम्प्राद्रवच्चमूः सर्वा धर्मराजस्य पश्यतः ॥

If we consider the age gap between Drona and Pandavas to be around 20 -30 years, then Arjuna’s age during the war could be 55- 65 years.

If we remove 13 years period of exile in the Forest from that age, at the time of game of dice the age of Arjuna could be 42 -52 years.

—

Shri Krishna was a few months older to Arjuna