The Problem with Shared Expenses
For many years, I experienced the same pattern whenever I traveled or attended parties and similar events with friends or family. Someone paid for dinner, someone else booked the cabin, and another person covered parking or gas. By the end of the trip, everybody vaguely agreed to “settle up later.”
Then came the spreadsheet, screenshots of receipts, Venmo requests, or the classic question: “Wait, who paid for that again?”
The bigger issue was not the math. Shared expenses are rarely divided equally. Maybe only a few people joined for dinner. One car may have paid for parking. The children’s snacks may not belong in everyone’s share.
Most tools I tried felt too rigid, unnecessarily complicated, or restricted by paid features.
Why I Built CostShare
I had two options. I could create a more sophisticated spreadsheet, add formulas, and keep revising it whenever a new situation appeared. Or I could use the opportunity to build a small app for myself.
That app became CostShare.
I am not a software engineer by trade. CostShare is intentionally a lightweight frontend application with no backend, accounts, or cloud infrastructure. I simply wanted something practical that worked well.
AI helped me develop it much faster than I could have on my own. The first working version took only a couple of days to assemble.
How CostShare Works
The process is intentionally simple:
- Add the people involved.
- Add each expense.
- Select who shared each cost.
- Let the app calculate balances and settlements.
CostShare also works well on mobile devices. Users can export spreadsheets, create printable summaries, and save or restore sessions for later use.
A Small Tool for a Real Need
I tested CostShare using the kinds of trips and group situations I have experienced myself. I expect to keep using it whenever friends or family share costs. If others find it useful too, even better.
You can try the CostShare app here.
None of this is a major technological achievement. People have managed shared expenses through spreadsheets, notes, calculators, and group chats for years. They will probably continue doing so.
CostShare simply made the process smoother for me. There is something satisfying about removing even a small amount of friction from an ordinary situation. Building a practical tool that I know I will personally use also felt like a worthwhile accomplishment.
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