Windsor Auction Calculator

Windsor Auction Calculator is a Windows desktop app built for Windsor Food Machinery Ltd. It prices food-machinery lots at Dutch auctions, where costs are kept in sterling and machines are sold in euro, and it replaces the Excel sheets the team used to do that by hand.

Each auction used to be a spreadsheet. Cost, reserve, sold price, profit and margin lived in formulas that people could overwrite, break or copy wrong. Exchange-rate mistakes and mixed sale types — machines the company owns versus machines sold on commission for a customer — made the totals unreliable.

One auction is now one file (.wfm.json). You type cost and target reserve in sterling; euro fills in beside them. You type the sold price in euro; sterling fills in beside it. Profit, margin and auction totals are calculated in code, so they cannot be edited like a cell formula.

There are two sale types. Owned stock: profit in sterling is the sold price converted to GBP, minus cost, and margin is that profit divided by the sold price in sterling. Customer commission: cost is ignored, and profit is the sold price in euro times the commission rate, converted to sterling. The default commission is 15%. A blank sold price means the lot is unsold, and profit and margin stay blank. Lots under a warning threshold (default 5% margin), or sold at a loss, are flagged.

The workspace is a home screen to start a new auction, open a file or reopen a recent one, and a machine grid for lot number, description, serial number, customer, cost, reserve, sold price, sale type, commission and notes. Rows can be added, duplicated or deleted, and filtered to all, owned stock, commission, unsold or low margin. A live dashboard shows machine count, unsold count, average margin, sterling and euro totals for cost, sold and gross profit, plus an income split between owned-stock profit and commission income, and a list of low-margin or loss-making lots.

Auction settings cover name, date, exchange rate (default 1.15), default commission and the low-margin threshold. Files can be saved, saved as, duplicated as a template, backed up, and exported to Excel or PDF. It ships with a Windows installer — desktop and Start menu shortcuts — and is currently at version 1.5.1.

It is an Electron desktop app with a React and TypeScript interface. The calculation engine is separate from the UI and covered by tests, Excel export uses ExcelJS, and each auction file is versioned JSON, so the numbers travel with the file and the formulas do not.

It is a real internal tool for a trading business, not a demo. The interesting part is replacing a fragile spreadsheet with a small desktop app that locks the money maths, handles two currencies and two sale types, and still feels like the sheet people already knew: type the inputs, read the margin, export the result.