Case study
Forex position sizing as a subscription product
A web application that does the position sizing and risk arithmetic a trader would otherwise do by hand, sold on a subscription with a free trial.
HFX
The challenge
Position sizing is arithmetic that has to be right every time and gets done under time pressure. A trader works out how much of an instrument to buy so that a stop-loss, if it is hit, costs a fixed percentage of the account. The calculation moves with the account currency, the instrument, the pip value, and the distance to the stop.
Most people do this in a spreadsheet they built themselves, or in their head. Both work until the moment they do not, and the failure is expensive in a way that is invisible until after the trade has closed. The arithmetic is also identical for every trader, which is exactly the sort of thing that should be a product rather than a personal spreadsheet.
The solution
A focused web application built around the calculations themselves rather than around a dashboard. A trader enters the account, the instrument, and the risk they are willing to take, and the position size comes back immediately.
The commercial side is part of the build rather than bolted on afterwards. Accounts, a free trial that converts without anyone having a support conversation, recurring subscription billing, and plan management all sit inside the same application. Building the trial and the billing at the same time as the product is what makes it a business rather than a tool.
What we delivered
- from brief to first release
- 8 weeks
- free trial, no card required
- 7 days
- trial to paid, with no sales call
- Self-serve
What this kind of build typically achieves
The commercial question for a product like this is what share of trials become paying customers, because that number decides whether the build pays for itself.
Opt-in trials that ask for no card up front convert in the region of 8 to 22 per cent, with a median near 14 per cent, according to published SaaS benchmarks for 2026. Lower-priced self-serve products sit at the higher end of that range, because one person can decide to buy without asking anyone.
That is why the trial and the billing were built alongside the product rather than after it. A trial that needs a human to convert it does not scale, and at this price point there is no room for one.
Figures above describe the sector, not this client. We publish a client’s own numbers only when they have measured and shared them.
What this involved
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