Currency Converter

Professional-grade currency converter using authoritative ECB reference rates. Convert between 30+ currencies, factor provider fees, and view historical rates.

Converter Inputs

Enter the amount, choose your currencies, optionally override the rate date, and simulate provider markdowns with the margin slider.

0.0% Simulates up to 5% provider markup

Adjusted rate = mid-market rate × (1 − margin). Use this to represent bank or card markups.

How to Use This Converter

Use the amount field together with the source and target currencies. Optionally select a historical rate date (holidays/weekends roll forward to the most recent ECB business day) and simulate provider markup using the slider. Press Calculate to refresh the results whenever inputs change.

Methodology

The tool requests ECB reference rates (via frankfurter.app) for the requested date. For non-EUR currency-to-currency conversions the calculator computes a cross-rate by dividing each currency's rate vs. EUR. Adjusted rates subtract the provider margin, keeping decimals consistent so results are deterministic across browsers.

All calculations strictly follow ECB data and the exact formulas shown in the Formulas section below.

Data Source and Notes

Authoritative data: European Central Bank (ECB) Euro foreign exchange reference rates (EXR), updated on TARGET business days. API mirror: frankfurter.app. Historical dates automatically roll to the latest available business day.

Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.

Worked Example

Example: convert 100 EUR to USD with a 1% provider margin. ECB quotes rEUR→EUR = 1 and assume rEUR→USD = 1.08. The cross-rate is 1.08, so:

Mid conversion: 100 × 1.08 = 108 USD.
Adjusted rate: 1.08 × (1 − 0.01) = 1.0692.
Converted amount: 100 × 1.0692 = 106.92 USD.
Fee impact: 100 × 1.08 × 0.01 = 1.08 USD.

Glossary of Variables

  • Amount (A): The quantity in your source currency to convert.
  • From currency (X): The currency you hold.
  • To currency (Y): The currency you want to receive.
  • Mid-market rate (rX→Y): Neutral rate without markup.
  • Provider margin (m): Percentage markup applied to lower the received rate.
  • Adjusted rate: rX→Y × (1 − m).
  • Converted amount (C): Final amount after applying the adjusted rate.
  • Fee impact (F): Reduction in the target currency due to the applied margin.
  • Rates date: ECB reference date used for the computation.

Frequently Asked Questions (FAQ)

Do you support historical exchange rates?
Yes; pick a date and the converter fetches the closest available ECB business day.

Why might my bank’s rate differ?
Banks/cards often add a margin. Adjust the slider to model that markup and watch the adjusted rate drop accordingly.

How many currencies are supported?
All ECB-published currencies accessible through frankfurter.app, including major and minor ones, plus the euro.

Is the converted amount guaranteed?
No, these results are for informational use. Providers' live quotes can vary by timing or additional fees.

What if there's no internet connection?
The tool will attempt to reuse previously cached rates and will warn if no fresh data is available.

Can I copy the results?
Yes; tap Copy results to copy a quick summary to your clipboard.

Authorship & Review

Strumento sviluppato da Ugo Candido. Contenuti verificati da CalcDomain Editorial Team.

Ultima revisione per l'accuratezza in data: .

Formulas

Let EUR-based rates be rEUR→X and rEUR→Y. The cross-rate from X to Y is:

rX→Y = rEUR→Y / rEUR→X

Given an amount A and margin m, the converted amount C is:

C = A × rX→Y × (1 − m)

The fee impact F is:

F = A × rX→Y × m

Citations

https://www.ecb.europa.eu/stats/eurofxref/ — ECB Euro foreign exchange reference rates (EXR), accessed 2026-01-19.

https://www.frankfurter.app/ — frankfurter.app mirror of ECB rates, accessed 2026-01-19.

Changelog

Version: 0.1.0-draft · Last code update: 2026-01-19

  • Initial audit spec draft generated from HTML extraction (review required).
  • Verify formulas match the calculator engine and convert text formulas to LaTeX.
  • Confirm sources are authoritative and relevant to the calculator methodology.
Verified by Ugo Candido Last Updated: 2026-01-19 Version 0.1.0-draft
Version 1.5.0