Probability of hitting a barrier calculator

In short

Touching is twice as likely as finishing beyond.

Interactive: probability of hitting a barrierMedium

Spot Barrier Volatility % p.a. Days to expiry

Distance to barrier: —
In volatility terms: —
Probability of touching: —
Probability of finishing beyond: —
Touch vs. finish: —
Reading: —

A 20% buffer over six months at 25% vol sounds generous and is not. This is the arithmetic behind every "the barrier is very far away" sales conversation — and behind the 2018 and 2020 case studies, where barriers assumed to be unreachable were reached.

The idea behind it

This calculator belongs to Volatility, where the mechanism it computes is explained step by step, with the formula, what each input means and where the simple model stops being right. Everything is computed in your browser; nothing you type is sent anywhere.

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All calculators

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The same in full — six points, and why each one matters

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The examples are simplified. Worked examples use round numbers and leave out costs, spreads, taxes, collateral, settlement and market conventions that materially change real outcomes.
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