Buhari, addressing a joint session of lawmakers in Abuja, said the spending was a 16 per cent increase over 2017 and aimed to "consolidate on the achievements of previous budgets and facilitate Nigeria's economic recovery."
He said critical sectors of the economy like roads, health, housing and job creation would be given priority next year.
"As a government, we are determined to bring succour to our people and deliver on our promises," he said.
Buhari came to office in May 2015 as global oil prices were plunging, ravaging the finances and economies of oil exporting nations like Nigeria, which depends on oil for 70 per cent of state revenues and 90 per cent of export earnings.
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Buhari said the budget was based on an estimated oil production of 2.3 million barrels per day as against 2.2 million bpd in the previous year.
The budget assumes a price of USD 45 dollars per barrel -- more than USD 15 per barrel less than the current price for the main international contract -- and an exchange rate of 305 naira to the dollar.
Buhari said 38 per cent of the budget would go to capital projects, while recurrent expenditure would be 3.49 trillion naira.