Compound Growth and Risk of Ruin Calculator

Two calculators, one screen: project what steady compounding actually does to a balance over time, then check the number that dream projection doesn't show you — the real probability that your risk-per-trade and win rate lead to ruin, not riches.

Why growth and risk belong on the same screen

Compound growth calculators are everywhere, and they're seductive for a reason — a modest per-period gain, compounded for a year, produces a chart that climbs into numbers that feel inevitable. What most of those calculators leave out is the other half of the same math: the same aggressive risk-per-trade that makes the growth curve steep is very often the exact setting that makes ruin likely, not unlikely. This calculator puts both numbers in front of you at once, so a growth projection can't be read without also seeing what it implies about your risk of blowing up trying to get there.

What's inside

• Compound growth projector Starting balance, gain per period, and a period unit of day, week or month, projected up to 520 periods — with final balance, total return and total gain
• Growth curve chart Linear or log scale, with the chart automatically defaulting to log once growth passes 20×, so the curve stays readable at any scale
• Milestone markers See exactly which period your balance crosses 2×, 5× and 10× your starting balance
• Share your projection One tap to share your starting balance, gain rate and projected result
• Risk of ruin calculator Win rate, risk per trade, average reward-to-risk and a ruin threshold you set, producing a risk-of-ruin percentage, expectancy in R, and a realistic longest losing streak
• Plain-English verdict A one-line read on whether your inputs describe a sustainable risk profile or a coin flip
• Private by design All calculations stay on your device — no account, no data collected

How the risk of ruin is calculated

This isn't a full trade-by-trade simulation — it's the classical closed-form gambler's-ruin result, applied by approximating fixed-fractional risk (a percentage of a balance that itself grows and shrinks trade to trade) as a fixed number of equal capital units. It's a well-established approximation, not a guess, and it comes with an honest caveat: real risk of ruin, once you account for position sizing that compounds and a sensible stopping rule instead of trading forever, is generally lower than what this calculator shows. Treat the number as a conservative upper bound on your risk, not a precise forecast.

Screenshots

Frequently asked questions

Is the risk of ruin number an exact simulation?

No — it's the classical closed-form gambler's-ruin approximation, treating fixed-fractional risk as a fixed number of equal capital units, rather than a full Monte Carlo simulation. Real risk of ruin with compounding position sizing and a stopping rule is generally lower than this approximation.

What counts as "ruin" in the calculator?

A drawdown threshold you choose yourself — for example 50% — not necessarily a complete loss of capital. You set the win rate, risk per trade, average reward-to-risk and the ruin threshold, and the app calculates the probability of hitting it.

Does the app store my numbers anywhere?

No. All calculations stay on your device — no account, no cloud, no data collected.

When will this app be available?

It's built and in final testing ahead of its Google Play submission. This page will switch to a Play Store link the moment it's live.

This app is a calculation tool for educational purposes. It does not provide financial, investment or trading advice. Trading involves risk.