Savings Calculator
Project a savings balance from initial deposit, monthly contributions, and an annual rate.
Written by Golam Rabbani, Founder & Lead Engineer
How to use this savings calculator
- Enter the initial deposit and pick a currency.
- Type the monthly contribution you plan to add (set 0 if you only have a lump sum).
- Enter the annual interest rate (%) and the horizon in years.
- Choose contribution timing: end of month (ordinary) or start of month (annuity-due).
- Press Calculate to see the future balance, total contributed, and interest earned.
- Tap Copy for a one-line summary, or Reset to model a different plan.
About this savings calculator
The savings calculator projects how a deposit and recurring monthly contributions will grow under monthly compounding. It applies two standard time-value-of-money formulas in tandem: the lump-sum future value FV_lump = P(1 + i)^N, and the future value of an annuity FV_annuity = PMT × ((1 + i)^N − 1) ÷ i, where i = annual rate ÷ 12 and N = 12 × years. For annuity-due (contributions at the start of the month) the annuity term is multiplied by (1 + i). These are the formulas given in the CFA Institute Time-Value-of-Money curriculum and the U.S. SEC's Investor.gov compound-interest worksheet.
Worked example: initial deposit USD 1,000, monthly contribution USD 200, annual rate 4.5%, 15 years, contributions at end of month. i = 0.045 ÷ 12 = 0.00375; N = 180. FV_lump = 1,000 × (1.00375)^180 ≈ USD 1,963.85. FV_annuity = 200 × ((1.00375)^180 − 1) ÷ 0.00375 ≈ USD 51,427.99. Future value ≈ USD 53,391.84; total contributed = 1,000 + 200·180 = USD 37,000; interest ≈ USD 16,391.84. Currency is a label only — there is no exchange-rate conversion.
FAQ
- What formula does the savings calculator use?
- FV = P(1 + i)^N + PMT × ((1 + i)^N − 1) ÷ i, with i = annual rate ÷ 12 and N = 12 × years. The annuity term is multiplied by (1 + i) for start-of-month contributions.
- What does "start of month" vs "end of month" mean?
- Start-of-month (annuity-due) contributions earn one extra month of interest each cycle, producing a slightly higher final balance. End-of-month (ordinary) matches most direct-deposit timing.
- Why is monthly compounding the default?
- Most savings accounts and certificates of deposit credit interest monthly. Daily compounding gives a tiny additional bump; annual compounding is rare for retail savings products.
- Does this include inflation or taxes?
- No. The projection is in nominal currency before tax. Subtract expected inflation from the rate to estimate the real-terms balance; deduct income tax separately if interest is taxable.
- What if the interest rate is zero?
- Then the future value is just initial deposit + monthly contribution × months. The calculator handles this edge case so it does not divide by zero.
- Is my information stored?
- No. The savings calculator runs entirely in your browser; nothing is uploaded.