Couples needed a better way to split bills fairly
Money arguments are the top predictor of divorce. Yet when couples search for a fair way to split shared expenses, the options are surprisingly poor. Splitwise has no income input at all. Proportional splitting was their most-requested feature for years, attracting over 1,600 votes, and it's still locked behind a paid tier. Budgeting apps like YNAB treat all household money as pooled, which doesn't work for couples who keep finances separate. The dedicated couples app, Honeydue, has no proportional splitting and shows signs of abandonment.
Most couples end up with a spreadsheet. It works until someone gets a raise, changes jobs, or goes on parental leave. Then they start from scratch. The gap in the market isn't better calculation or better tracking. It's the space between the two, where couples calculate their split once and then struggle to maintain it with disconnected tools.
I built Fair Share Calculator to close that gap, starting with the part everyone gets wrong: making the initial split effortless.
A spreadsheet that became a product
When my partner and I moved in together, we wanted money handled fairly. We found proportional splitting, where each person pays a share of expenses based on their income, and built a spreadsheet to do the maths. It worked, but pulling up Excel on your phone to split dinner got old fast.
I'm a UX designer. I saw the friction and figured I could build something better.
Pulling up Excel on your phone to split dinner got old fast.
Built with the tools I grew up on
I started with HTML, CSS, and JavaScript. Not because they were the right stack for a product, but because they were the tools I understood. I'd been writing CSS since customising my MySpace page as a teenager, and that comfort meant I could focus on the experience rather than fighting the code.
This was early 2023. ChatGPT had just launched and I had enough front-end knowledge to prompt my way through the gaps. I vibe coded a simple calculator, hosted it on a default GitHub Pages URL. Ugly, but functional. We could pull it up at the shops, split groceries, and move on.
Once it had real users and I could see where the product needed to go, I migrated to Next.js, React, and Supabase. The goal was to set up for features that need authentication and persistent data, things like saved calculations and returning user experiences. The migration was straightforward because I'd kept the front-end logic clean from the start.
Every feature came from someone using it
The UX designer in me couldn't leave it alone, but I wasn't just polishing. Every meaningful change came from real feedback.
Originally you could only split one expense at a time. Users told me they wanted to enter all their shared costs at once and label each one. So I built multi-expense input with custom labels. You could name each salary too, so instead of "Salary 1" and "Salary 2" the names carry through to the results page.
I added localStorage so the calculator remembered your figures between visits. Made sure the number keypad appeared on mobile instead of the full keyboard. Supported 8 currencies with automatic detection. Added the option to hide salary amounts for couples who aren't ready for that conversation yet.
I also built a share feature so couples could send their results to each other. After six months, the data showed minimal usage. Most people were on mobile and just screenshotting the results page. So I removed the share feature and instead optimised the results layout to be clear and screenshottable. That's a trade-off I'm glad I made.
People also asked why proportional splitting is fair, or how the maths works. I added an FAQ addressing those questions directly, and wove an explanation into the results page so the "why" is visible at the moment it matters most.
The data told me what users actually did, not what I assumed they'd do.
Organic growth through search intent
I got a proper domain, set up Google Analytics and Search Console, and then mostly forgot about it. It grew on its own. No ads, no social media, no marketing budget. Just people searching for a fair way to split bills and finding Fair Share.
The inflection point came from the FAQ. I used Google Search Console to find keywords where Fair Share appeared in results but wasn't getting clicks. Questions like "how to split rent by income" and "proportional expense splitting calculator." I wrote FAQ content targeting those exact queries, and traffic climbed.
The growth is entirely organic. 91% of traffic comes from first-time visitors finding the tool through search at the exact moment they need it. That acquisition model is self-sustaining because proportional splitting is a phase most couples enter when they move in together, and new couples are always entering that phase.
91% of traffic comes from first-time visitors finding the tool at the exact moment they need it.