Trip Expense Splitter Desktop App with Settlement Optimization and Currency Support

A trip expense splitter is a desktop app that records what each traveller paid, converts every expense to one base currency, splits each cost fairly, and works out who owes whom. This project builds one for group trips: it takes multi-currency expenses, nets each person's paid amount against their share, and outputs the smallest set of repayments that settles everyone.

Group trips usually end in a messy spreadsheet: one person paid the hotel, another booked flights in dollars, a third covered food in euros, and suddenly everyone owes everyone else a different amount. The Trip Expense Splitter Desktop App replaces that spreadsheet with one local app. Travellers are added once, each expense is entered in the currency it was actually paid in, and the app converts it to the trip's base currency at a rate the organiser enters by hand. It totals what each person paid, subtracts their fair share, and nets the result into a single balance per person. Then it matches the largest amounts owed against the largest amounts owing, producing the smallest set of repayments that settles the whole trip. No data is sent to a server, and no money moves inside the app.

Using the Trip Expense Splitter Desktop App is a straight line from trip setup to a settled group. The organiser adds the travellers, then logs each expense with its payer, amount and original currency, and the app converts it to Indian Rupees at the manual rate on file. Every expense is split equally across the current members, so each person's share grows as expenses are added. The app then subtracts each member's total share from their total payments to get one net balance per person — positive for members the group owes, negative for members who still owe. A greedy matching step pairs the largest debtor with the largest creditor, takes the smaller of the two amounts, and repeats until every balance is zero. The resulting list is the settlement plan, which the group works through outside the app and marks recorded as each transfer is done.

1. Add the travellers who will share the trip's costs.
2. Log each expense with a description, the member who paid, the amount, and the currency it was paid in.
3. The app converts each expense to INR using the organiser-entered manual rate for that currency.
4. Each expense is split equally across the current members, building each person's total share.
5. The app computes one net balance per member: total paid minus total share.
6. Creditors and debtors are matched largest-first; each match becomes one transfer for the smaller of the two amounts, repeated until all balances reach zero.
7. The group pays each transfer outside the app, marks it recorded in the plan, and exports the balances and plan as a CSV file.

Tech stack:

• HTML · CSS · JavaScript (single-file desktop-style app)
• Local browser storage (no server or account)
• CSV export (balances and settlement plan)
• Greedy largest-first settlement algorithm
• Manual multi-currency conversion (INR base)
• Git (version control)

The Trip Expense Splitter Desktop App centres on four capabilities: multi-currency expense entry, per-person net balances, a minimum-transfer settlement plan, and CSV export of the final record. Multi-currency entry lets each expense stay in the currency it was paid in, converted to Indian Rupees at a rate the organiser types in, so a dollar flight and a euro grocery bill sit in one honest total. Net balances collapse every member's payments and shares into one figure — owed or owing — instead of a tangle of pairwise debts. The settlement plan then matches the largest debtors to the largest creditors first, producing the fewest transfers that can settle the trip. CSV export turns the finished balances and plan into a file the group can keep, print, or attach to a report.

• [Multi-currency expense entry] Each expense is recorded in INR, USD, EUR or GBP with the payer and a description, and converted to the INR base at the organiser's manual rate, shown beside the original amount.
• [Per-person net balances] For every member the app totals amounts paid, subtracts their equal share of every expense, and shows one net figure: is owed, owes, or settled at zero.
• [Minimum-transfer settlement plan] A greedy largest-first match between creditors and debtors produces the smallest set of repayments; the demo trip settles in 3 transfers instead of up to 15 expense-by-expense shares.
• [Member management] Members can be added at any time, and later expenses split across the new group size; the demo trip starts with 4 travellers.
• [Editable manual exchange rates] The organiser can change the USD, EUR and GBP rates to INR, and every converted total, balance and transfer updates immediately.
• [Settlement recording] Each planned transfer can be marked as recorded once the group has paid it outside the app; the record is a log entry only and moves no money.
• [CSV export] Balances and the settlement plan export to a CSV file for the group's records or for inclusion in the project report.

Optional customization: custom share weights per expense (unequal splits), additional currencies, and multi-trip history can be added on request. Future scope: fetched live exchange rates, a UPI payment link for each transfer, and a native installable desktop build are future scope, not part of the base project.

Builder note from the demo build: the settlement edge case that shaped the design is a member who both pays and shares — Priya pays ₹44,640 across two expenses while also sharing every expense, yet she appears once in the plan as a single net creditor of ₹23,880, not once per expense. Netting before matching is what makes the 3-transfer plan possible; matching per expense would have produced up to 15 transfers.

• Complete single-file desktop-style demo app (member, expense, balance, settlement and CSV export features)
• Project report PDF (background, methodology, settlement algorithm, limitations)
• PPT presentation for final review
• Viva Q&A preparation document (netting, greedy matching, currency conversion, limitations)
• Setup and demo walkthrough guidance
• Next step: message on WhatsApp for a quotation stating scope (desktop trip expense splitter with multi-currency entry at organiser-entered rates and a minimum-transfer settlement plan), as a built-to-order project with no fixed price