How to Calculate Interest on Monthly Loans (Annuity)

  • Most loans use monthly payments — not simple interest.
  • Use this formula: Monthly Payment = P × [r(1 + r)^n] / [(1 + r)^n – 1]
      P = loan amount,
      r = monthly interest rate (annual rate ÷ 12 ÷ 100),
      n = number of months.
  • Example: Borrow ₦100,000 for 12 months at 24% → r = 0.02
  • Monthly Payment ≈ ₦9,392 → Total repayment = ₦112,704 → Interest ≈ ₦12,704
  • Simple interest would say ₦12,000 — but annuity adds more.

👉 Don’t guess your repayment — use the right formula.