Compound-Growth Illustration

How this calculation works

How do repeated contributions and a constant growth rate change a starting pot?

Formula in plain language

• Let r = growth percentage ÷ 100 and C = contribution per period.
• End-of-period contributions: next balance = current balance × (1 + r) + C.
• Start-of-period contributions: next balance = (current balance + C) × (1 + r).
• Total contributed = starting amount + C × periods; illustrated growth = ending balance − total contributed.

What the terms mean

Per-period rate

The rate belongs to each selected interval. A monthly rate is not an annual rate, and no calendar frequency or annual-rate conversion is applied here.

Contribution timing

Start contributions receive that period's modeled growth; end contributions do not. Enter a whole number of periods.

Explicit zero

Zero growth is valid: only contributions change the pot. This model accepts non-negative growth, not a sequence of fluctuating or negative returns.

Worked example

This is a fixed teaching example, separate from your current inputs.

Choose USD, starting amount 100, contribution 10, periods 2, growth 10% per period and End of each period. The high rate is only for easy arithmetic.

1. Period 1: 100 × 1.10 + 10 = USD 120.
2. Period 2: 120 × 1.10 + 10 = USD 142.
3. Total contributed: 100 + 10 × 2 = USD 120; illustrated growth: 142 − 120 = USD 22.
4. With Start of each period instead: (100 + 10) × 1.10 = 121, then (121 + 10) × 1.10 = USD 144.10.

Example result: USD 142.00 ending balance, USD 120.00 contributed and USD 22.00 illustrated growth for end timing.

What the result means

Separate money you put in from modeled growth. A bigger final pot is not all investment gain, and contribution timing changes how long each addition receives growth.

What this does not tell you

Constant growth is a mathematical assumption, not an expected return. Fees, inflation and taxes are excluded; real returns fluctuate and may be negative. Do not use this illustration as a promise of wealth.