Plate 12 · Calculator

Growth calculator

Test a scenario before you commit money to it. Enter a starting amount, a monthly contribution, and a growth rate you choose. The calculator shows what that assumption would produce over time.

Amounts appear in your own currency without a symbol. The growth rate is hypothetical. It is not a forecast for bitcoin or for any other asset.

Plate 13 · Reading the numbers

How to read the result

Projected value is what the scenario produces at the end of the chosen period. Total you contributed is what you put in yourself. Growth earned is the difference between the two.

Value in today's money shows the projected value after adjusting for the inflation rate you enter, so you can compare it with what the starting amount buys today.

Plate 14 · Inputs

Your scenario

Starting amount

The money you begin with. Type an exact figure, or move the slider for a quick change.

Monthly contribution

Added at the end of each month, after that month's growth.

Assumed annual growth rate (%)

A rate you choose for the what-if. Zero means no growth. It is not a prediction for any asset.

Years

How long the scenario runs, from 1 to 40 years.

Assumed inflation (%)

Used only for the today's-money figure. Set zero to leave it out.

Live updates need JavaScript. The figures shown are for the example scenario. With JavaScript on, the results, chart, and table recalculate as you change the inputs.

Plate 15 · Output

Projected result

Projected value: 20,171
Total you contributed: 13,000
Growth earned: 7,171
Value in today's money: 15,009

After 10 years at an assumed 8% annual growth rate, the projection is 20,171, from 13,000 contributed. This is a what-if scenario, not a forecast.

Plate 16 · Path

The path, year by year

Projected value as a solid green line and total contributed as a dashed line, by year. The table below gives the same figures.

Projected value
Total contributed

Plate 17 · Table

Year by year

Year-end figures for the current scenario, in your own currency.
Year	Total contributed	Projected value
0	1,000	1,000
1	2,200	2,323
2	3,400	3,753
3	4,600	5,296
4	5,800	6,963
5	7,000	8,764
6	8,200	10,708
7	9,400	12,808
8	10,600	15,076
9	11,800	17,526
10	13,000	20,171

Plate 18 · Method

The arithmetic

The annual rate is converted to an equivalent monthly rate, so growth compounds every month. Each month the balance grows by that monthly rate, and then the monthly contribution is added at month end.

Inflation is handled separately. The projected value is divided by one plus the inflation rate, raised to the number of years, to express it in today's money.

The model leaves out taxes, fees, withdrawals, pauses in contributions, and the uneven path a volatile asset actually follows. A steady rate hides risk. Treat the output as a lesson in arithmetic, not as a forecast.