Legacy Investing CalculatorsShow

Compound savings growth

What can recurring savings become over time?

Your numbers

$
$
%
yrs

Future value

$373,137

Total contributed$159,000
Growth$214,137

Tip. Try 5%, 7%, and 9% return cases instead of committing to one optimistic number.

Assumptions

  • Monthly compounding at annual rate ÷ 12.
  • Contributions at month end. No fees or taxes.

Explore the numbers

Examples and charts

Start with a scenario, then read the response curve to see which input actually moves the answer.

Example 1

Building the habit

A modest start with twenty years of steady deposits.

Future value

$176,472

Example 2

Core plan

A $15,000 start, $600 a month, at a 7% illustration rate.

Future value

$373,137

Example 3

Cautious return

The same plan at 5%, which is the case worth checking before you rely on the number.

Future value

$287,310

Sweeps monthly contribution from half to one and a half times your value, holding everything else fixed.

Response curve

How monthly contribution moves the result

Future value

$373,137

$200k$250k$300k$350k$400k$450k$500k$550k$400$600$800
Chart axis: Monthly contributionNow $600 → $373k

Timeline

Balance vs the money you put in
$0$100k$200k$300kNowY10Y20
  • Balance
  • Money you put in

What this calculates

Projects a starting balance plus monthly contributions with monthly compounding. Good for long-horizon investing illustrations, and not a promise of returns.

How to use it

  1. Start with starting balance and work down the form, or load an example to begin from a realistic case.
  2. Read the headline result alongside the supporting rows, which show the intermediate figures behind it.
  3. Check the assumptions. They decide what the number includes and, more importantly, what it leaves out.
  4. Sweep monthly contribution on the response curve to see how much it actually moves the answer.
  5. Run a cautious case as well as an optimistic one before using the estimate in a decision.

Common mistakes

  • Treating the ending balance as a sure thing.
  • Modelling contributions you cannot actually sustain through a bad year.
  • Comparing a nominal projection here to a real-dollar goal somewhere else.

Formula

Each month: B ← B(1 + r/12) + contribution

Inputs

  • Starting balance
  • Monthly contribution
  • Expected annual return (%)
  • Years (yrs)

FAQ

Is 7% a guarantee?

No. It is a common long-run illustration rate for a diversified stock portfolio before inflation. Actual returns vary enormously year to year and the order they arrive in matters.

Are fees and taxes included?

No. Pair this with the investment fee drag calculator to see what an expense ratio does over the same horizon.

Should I use a real or nominal return?

If you enter a nominal rate like 7%, the ending balance is in future dollars. Subtract expected inflation, so use about 4 to 5%, if you want the answer in today's buying power.

Why does the timeline chart bend upward instead of running straight?

Because growth compounds on growth. The gap between the balance line and the contributions line is the return doing the work, and it widens every year.

Are these numbers financial advice?

No. They are educational estimates based on the inputs and assumptions on this page. Confirm important decisions with a qualified professional and your own documents.

Read the full guideCompound interest savings guide

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