Integrations · exchange rates · Excel
An import cost calculator with live exchange rates and Excel export
Client:
Import and wholesale, NDA
Category: Integrations
Stack: JavaScript, SheetJS (xlsx), PHP (curl_multi), exchange rate API, HTML/CSS
Timeline: about 4 weeks
Problem
The cost of imported goods was calculated in a spreadsheet by hand: exchange rates were copied from websites, and delivery, duty and markup were estimated for each item separately. One formula error — and the sales team got the wrong price.
Constraints
Suppliers price in dollars, euros, rubles and yuan, but the calculation has to be in tenge; the external rate service may not respond, and its access key must not be exposed to the browser.
What I did
- Item cards: price, currency (USD, EUR, RUB, CNY) and quantity; all amounts recalculate instantly on any change
- Delivery defaults to 6% of the goods amount and can be entered manually in euros when needed
- The calculation chain: duty, additional costs, overhead contribution, trade markup, price excluding VAT and the manager bonus — in blocks for the administrator and the sales team
- Rates of four currencies to tenge — parallel requests (curl_multi) through a PHP proxy, so the API key stays on the server; ruble and yuan via a cross rate through the dollar
- Three attempts to fetch rates with a pause; on failure — default values and manual editing of any rate
- Exporting the calculation to .xlsx via SheetJS: a formatted table with amounts in tenge and the cost of each item
Architecture
Item form (JS)
→ PHP rate proxy (curl_multi)
→ Exchange rate API
→ Cost calculation
→ .xlsx export (SheetJS)
Result
Cost and selling price for each item are visible as soon as they are entered: rates load automatically, and the finished calculation is exported to Excel with one button. The calculator was released in March 2025.
What can be reused
Parallel rate loading via curl_multi with cross rates
Retries with fallback to manual input
Browser-side export of a tabular calculation to .xlsx