Compound calculator | Tool-Lifes

Defaults are teaching numbers, not a forecast. Change any input to see which lever moves terminal wealth most.

Educational illustration — not advice, a quote or a guarantee.

Scenario gallery

Teaching presets — tap to load inputs, then tweak. Not forecasts.

Goal-gap snapshot

Save a named snapshot of the goal already on this calculator against the current levers. The rail shows which single lever closed more of the gap than the others — teaching illustration, not advice.

Educational scenarios only. Not a forecast, a product offer or personalised financial advice.

Snapshot name

Snapshot A—

Snapshot B—

Growth instrument

Sticky levers + live curve — teaching model, not advice.

Nominal vs real growth

Nominal balance428,336
Real (inflation-adj.)255,057
Total contributions108,000
Rule of 72 doubling years10.3

Nominal balance Real (inflation-adj.) Total contributions

Scenario A / B

Two lives on one chart — change one lever at a time.

Nominal A vs B

Goal-seek years

Solve for years to reach a target balance (teaching model, not advice).

Target balance

Printable year table

Year-by-year teaching table from the levers above. Not a loan schedule and not advice.

Year	Start	Paid in	Net growth	End (nominal)	End (real)
1	10,000	3,600	816	14,416	14,102
2	14,416	3,600	1,126	19,142	18,383
3	19,142	3,600	1,457	24,199	22,851
4	24,199	3,600	1,812	29,611	27,515
5	29,611	3,600	2,192	35,403	32,384
6	35,403	3,600	2,598	41,601	37,465
7	41,601	3,600	3,033	48,234	42,769
8	48,234	3,600	3,498	55,333	48,304
9	55,333	3,600	3,996	62,929	54,082
10	62,929	3,600	4,529	71,059	60,113
11	71,059	3,600	5,100	79,759	66,408
12	79,759	3,600	5,710	89,069	72,979
13	89,069	3,600	6,363	99,032	79,837
14	99,032	3,600	7,062	109,695	86,995
15	109,695	3,600	7,811	121,105	94,466
16	121,105	3,600	8,611	133,316	102,264
17	133,316	3,600	9,468	146,384	110,404
18	146,384	3,600	10,385	160,369	118,900
19	160,369	3,600	11,366	175,334	127,767
20	175,334	3,600	12,416	191,350	137,023
21	191,350	3,600	13,539	208,490	146,684
22	208,490	3,600	14,742	226,832	156,767
23	226,832	3,600	16,029	246,460	167,292
24	246,460	3,600	17,406	267,466	178,278
25	267,466	3,600	18,880	289,946	189,744
26	289,946	3,600	20,457	314,003	201,712
27	314,003	3,600	22,145	339,748	214,204
28	339,748	3,600	23,951	367,299	227,243
29	367,299	3,600	25,884	396,783	240,852
30	396,783	3,600	27,953	428,336	255,057

Net growth is end minus start minus contributions, after the fee in the model. Monthly deposits are summed to the year.

Embed this calculator

Copy the iframe for blogs or classrooms. Educational only — not advice. Page is noindex.

<iframe src="https://tool-lifes.com/compound/en/calculator/embed/" width="100%" height="420" style="border:1px solid #e2e8f0;border-radius:12px" loading="lazy" title="Compound calculator"></iframe>

Frequently asked questions

Is this calculator financial advice?

No. Outputs are educational scenarios, not personalised advice or a forecast.

Why include fees and inflation?

Gross returns overstate what compounds for you. Net rate and real purchasing power are the levers that matter.

What does the Rule of 72 number mean?

It estimates years to double at a constant rate (72 ÷ rate %). It ignores fees, inflation and changing contributions.

How should I use the scenario gallery?

Load a teaching preset, then change one input at a time to see which lever moves terminal wealth most.

Worked example with the printed defaults

Principal 10,000, 300/mo, 7%, 30y, 0.2% fee, 2.5% inflation — teaching only.

Printed defaults — 10 000 principal, 300 monthly, 7% rate, 30 years, 0.2% fee, 2.5% inflation on load.
Years and contributions win — Often beat a 1-point rate tweak on this baseline.
Nominal vs real — Real line applies 2.5% inflation teaching.
Fees nibble real — 0.2% annual fee on the net path — illustrative.
Goal-gap second scenario — Snapshots A/B compare saved inputs, not advice.

At 7%, Rule of 72 ≈ 10.3 years to double — ignores fees, inflation and changing contributions.

Educational illustration only. Not financial advice.

Second what-if: double the monthly contribution

After the printed-default walkthrough, keep 10 000 / 7% / 30y and compare 300/mo vs 600/mo — teaching only.

Hold principal and rate — Leave 10 000 principal and 7% rate fixed from the printed defaults.
Double the monthly line — Move contribution from 300 to 600. Watch years and contributions beat a 1-point rate tweak on this baseline.
Re-read nominal vs real — Keep 2.5% inflation teaching on the real line so the second scenario stays honest.
Optional goal-gap snapshot — Save A at 300/mo and B at 600/mo — compare inputs, not advice.

On these defaults, doubling the monthly contribution is a second worked decision before you chase a higher rate.

Educational illustration only. Not financial advice.

Three worked totals

Pick one teaching scenario. Principal 10,000, 30 years, monthly compounding.

300 / month at 7% 600 / month at 7% 300 / month at 8%

Nominal total is 447,156. Doubling at 8% would take about 9.0 years; this row does not use that rate.

Illustration only. Not financial advice.

How to read this calculator

Are these numbers a forecast or financial advice?

No. Defaults on this page are teaching values: start 10,000, 300 a month, 7% annual return, 30 years, 0.2% fee, 2.5% inflation. The disclaimer already says the outputs are educational scenarios, not personalised advice.

Which lever usually moves the end balance most?

Change one input at a time. Years and the monthly contribution typically dwarf a small rate tweak; fees and inflation cut the real (inflation-adjusted) line. The goal-gap snapshot compares two scenarios you save on this page.

Why is the contribution monthly if the rate is annual?

The page already states it: contributions are monthly; return, fee and inflation are annual rates compounded monthly. That matches the chart, not an annual lump-sum example.

What does goal-seek answer?

It solves for years to a target you type, using the same teaching model as the main form. It is not a retirement plan. If the target is out of range, the page reports that it cannot solve.

Should I read the nominal or the real balance?

The chart draws both. Nominal is the raw balance; real subtracts the inflation input. A high nominal can still lose purchasing power if inflation is high — that is the teaching point, not a forecast.

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