About This Calculator
Use this free CD interest calculator to estimate your maturity value based on principal, APY, term length, and compounding frequency. All calculations run locally in your browser.
How to Calculate CD Interest
- Enter your initial deposit (principal), APY, term in months, and compounding (monthly/quarterly/annual)
- Click Calculate or adjust inputs to see instant results
- Review maturity value, total interest earned, and effective annual yield
Formula and Method
We use your APY and compounding to estimate maturity value.
- Periods per year (n): Monthly = 12, Quarterly = 4, Annually = 1
- Periodic rate (r): r = (1 + APY)^(1/n) - 1
- Total periods: periods = (months / 12) * n (can be fractional)
- Maturity value: M = P * (1 + r)^(periods)
- Interest earned: I = M - P
We round currency to the nearest cent to reflect real-world statements.
Worked Example
Principal P = $10,000; APY = 5.00%; Term = 12 months; Compounding = Monthly.
- n = 12; r = (1 + 0.05)^(1/12) - 1 ≈ 0.004074
- periods = (12 / 12) * 12 = 12
- Maturity: M = 10000 * (1 + 0.004074)^12 ≈ $10,511.62
- Interest: I ≈ $511.62
Note: Daily compounding would yield slightly more, but APY already summarizes compounding.
Why Use This CD Calculator?
- Free: Completely free—no signup, no ads required to calculate
- Private: Runs 100% in your browser. We don’t store your inputs
- Fast: Instant results as you type
- Simple: Clean, mobile-first UI
- Mobile-Friendly: Optimized for small screens and touch
What’s Calculated
We estimate maturity value using your APY and compounding frequency. For non-integer months, the calculation prorates the final period. Results are rounded to the nearest cent for clarity.
Common Pitfalls
- APY vs APR: APY includes compounding and is appropriate for CDs.
- Partial months/years: We prorate using fractional periods for a closer estimate.
- Daily compounding: Actual results may differ slightly; APY normalizes most differences.
- Taxes and penalties: This tool shows pre-tax estimates and excludes early withdrawal penalties.
Early Withdrawal: Should You Cash Out?
- Estimate what you've earned so far and the penalty per your bank's policy (e.g., 3 or 6 months of interest).
- Compute net interest (earned minus penalty) and your refund amount.
- For the remaining term, calculate the break-even APY: if a new CD's APY exceeds this, switching could make sense. Otherwise, holding likely yields more.
Tip: Penalties are often based on interest, not principal—our calculator approximates typical policies.