Savings Calculator – Compound Growth

Savings grow from two engines: the lump you already hold compounds on itself, and every recurring deposit builds its own annuity. The calculator adds both parts — the future value of the initial balance P(1+r)^n and the future value of monthly deposits PMT × ((1+r)^n − 1)/r, where r is the monthly rate and n the number of months. Example: starting with 5,000 and adding 300 per month at 4% annual (r = 0.00333) for 10 years (n = 120) gives (1.00333)^120 ≈ 1.4908, so FV = 5,000 × 1.4908 + 300 × 0.4908 ÷ 0.00333 ≈ 7,454 + 44,175 ≈ 51,629. Of that, 36,000 is your own money — deposits plus start — meaning about 15,600 is earned interest. Raising the monthly deposit by 100 adds roughly another 14,700 over the same decade.

1. 1

   Step 1

   Enter your current savings balance as the starting lump P.

2. 2

   Step 2

   Enter the monthly deposit and the annual interest rate (savings APY).

3. 3

   Step 3

   Enter the horizon in years; n becomes years × 12.

4. 4

   Step 4

   Read the future value split into deposits and interest earned.

• Ignoring compounding frequency

• Forgetting inflation

• Stopping deposits early