Finanz-Kids

Finanz-Kids brings the math behind interest, stock options, crude oil
futures, and home loans to life — using the same models real financial
markets use.

Four calculators, one goal: understand how financial products are
actually priced, not just memorize formulas.

COMPOUND INTEREST CALCULATOR
Enter starting capital, monthly contribution, interest rate, and term —
instantly see how powerful compound interest becomes over the years.
Optionally factor in inflation and your personal tax rate to see what is
really left in today's money after tax.

STOCK OPTIONS (BLACK-SCHOLES-MERTON)
The classic option pricing model — and you do not have to look up a single
number. Pick a stock from the list (Apple, NVIDIA, Tesla, Coca-Cola, and
more) and the price, the dividend yield, and the historical volatility of
the last 250 trading days are filled in at once. Alongside them come the
real expiry dates and, if you want, the real strike prices with the current
bid and ask quotes from the options exchange.

The moment it clicks comes next: choose a strike and the app fills in that
option's market price, then works backwards to the volatility the market is
assuming. Historical and implied volatility sit side by side — and you see
at a glance that the market often expects something quite different from
what history alone would suggest.

Everything can still be entered by hand, of course: your own ticker symbol,
your own expiry date, your own value in every field. The intermediate values
d1 and d2 are shown as well, and the risk-free rate is taken from the
current US Treasury yield curve to match the time to expiry.

FUTURES OPTIONS (WTI CRUDE OIL, NYMEX)
Price options on WTI crude oil using the Black-76 model — plus a
binomial tree (Cox-Ross-Rubinstein) for American-style early exercise,
exactly as traded on the NYMEX. The current futures price loads live,
and the "early exercise premium" shows the difference between both
models directly. You can also work backwards from a market price to the
implied volatility.

MORTGAGE CALCULATOR
How does an annuity loan actually work? Enter loan amount, interest rate,
initial repayment rate, and fixed-rate period to see the monthly payment,
the remaining debt at the end of the fixed-rate period, and the
year-by-year amortization schedule including cumulative interest and
principal. Assume a new interest rate to play through what happens once
the fixed-rate period ends.

EVERY TERM EXPLAINED
Next to every input field sits an info button. One tap brings up a plain
explanation — what volatility actually measures, why the finance industry
annualizes it, what contango and backwardation mean, how a tax-free
allowance on investment income works. Eighteen topics, each with a concrete
worked example and cross-links to related terms. Nothing to look up
elsewhere: the explanation sits exactly where the term first appears.

THREE LANGUAGES
The interface and all eighteen explanations are available in English,
German, and Traditional Chinese, switchable at any time. The displayed
currency can be chosen separately.

WHO IS THIS APP FOR?
For students and anyone looking for a hands-on, tangible introduction to
financial valuation — no background in stochastic calculus required, but
built on the real formulas instead of oversimplified approximations.

PRIVACY
Finanz-Kids collects no personal data whatsoever. No user accounts, no
ads, no in-app purchases, no tracking. Inputs stay temporarily on your
device only.

DISCLAIMER
This app is for educational and demonstration purposes only. Calculated
values are model outputs and do not constitute investment or financial
advice.