Overview
A savings-growth calculator that compounds a starting amount plus regular monthly contributions at a rate and compounding frequency you choose. It reports the future value, the total you personally put in, the interest earned, and a growth multiple, so you can separate your own deposits from what compounding added.
How It Works
Set a starting amount and a monthly contribution, drag the annual-return slider from 0 to 20 percent, and pick a horizon of 1 to 45 years. Choose a compounding frequency — monthly, quarterly, yearly, or daily — and the four outputs update: future value, total invested, interest earned, and the growth multiple of everything you put in. Everything recalculates live as any input moves.
Step-by-Step Usage Guide
- Enter your starting balance and planned monthly contribution.
- Choose an annual return assumption on the slider.
- Set the time horizon in years.
- Compare the future value against total invested to see what compounding contributed.
Technical Specifications & Standards
The model does one consistent thing: it converts your nominal rate and chosen frequency into an effective annual rate, effective annual = (1 + r/m)^m − 1, then derives an equivalent monthly rate as (1 + effectiveAnnual)^(1/12) − 1. The principal compounds at the effective annual rate and the monthly contributions compound at the equivalent monthly rate, which keeps the two parts of the projection on the same footing regardless of whether you select daily or yearly compounding. Because the contribution path always compounds monthly internally, choosing quarterly versus monthly changes the result less than most people expect — the frequency selector mostly affects how the nominal rate is interpreted. The arithmetic assumes a constant return, contributions made every month without fail, no fees, no taxes, and no inflation. At 7 percent over 15 years, a 10,000 start plus 500 a month projects to roughly two and a half times the invested total — a useful illustration, not a promise. The output is an estimate for planning conversations, not investment advice.
Targeted Use Cases
- Projecting a savings account or fixed-deposit-style balance at a known rate.
- Seeing how a small rise in monthly contributions changes a 20-year outcome.
- Demonstrating why daily versus yearly compounding barely moves long-horizon results.
- Setting a target: adjust contributions until the future value fits a goal.
Notes & Gotchas
- Use a return assumption you can justify; the slider maxes at 20 percent for a reason.
- Compare the growth multiple across horizons to internalise how the last years contribute most.
- Subtract expected inflation mentally — a nominal projection is not purchasing power.
- Rerun the numbers whenever your contribution changes; the model is only as current as its inputs.
Frequently Asked Questions
How does the compounding frequency affect the result?
The tool converts the nominal rate to an effective annual rate using (1 + r/m)^m − 1 for your chosen m, then compounds both the principal and the monthly contributions on that basis. Daily versus monthly compounding changes the outcome only slightly; the rate and horizon matter far more.
Does the tool model market volatility?
No. It applies one constant rate for the entire horizon. Real investments fluctuate, and the order of good and bad years changes outcomes for money you add over time. Use the projection as a planning illustration, not a forecast.
What is the growth multiple?
Future value divided by total invested. A multiple of 2.50x means the projected balance is two and a half times everything you put in, with the remainder being accumulated interest.
Is this financial advice?
No. It is a deterministic arithmetic model of the rate you enter. It ignores fees, taxes, inflation, and risk, and it does not recommend any product. For decisions, consult a qualified adviser.