Simple or compound — total interest and final balance in one click.
Demand 0.2% · 1-year 1.45% · 3-year 1.95% · 5-year 2.0%. Actual rates vary by bank — always confirm with your bank.
P = principal, r = annual rate (as decimal), t = years. For monthly compounding use (1 + r/12)^(12t).
Simple interest pays only on the principal: I = P × r × t. Compound interest pays on principal plus accumulated interest: A = P × (1 + r)ᵗ. Over long periods compounding grows dramatically faster.
Simple: 100,000 × 3.5% × 3 = ¥10,500. Compounded annually: 100,000 × (1.035³ − 1) ≈ ¥10,872 — about ¥372 more.