For corporate treasury teams
Verify the interest your bank charges — independently, in minutes
Since LIBOR ended, floating-rate interest is built from dozens of daily overnight fixings, compounded with lookbacks, shifts and day-count conventions. Your bank sends one number. This calculator rebuilds that number from official central-bank data so you can check it — free, with no sign-up, and nothing stored.
How it works
Enter your facility terms
Principal, interest period, spread/margin, lookback period, and convention (with or without observation shift) — straight from your facility agreement or rate-fixing advice.
We pull the official rates
Daily benchmark fixings come directly from the NY Fed (SOFR), Bank of England (SONIA), ECB (€STR) and Bank of Japan (TONAR) — the same sources your bank uses. No manual rate entry, no stale data.
Compare, line by line
Get the full daily ledger — every fixing, day-weight, and accrual — plus the effective rate and total interest. Export to Excel or PDF and reconcile it against your bank's interest advice.
Accuracy you can defend internally
The compounding engine reproduces the New York Fed's own published 30-day compounded SOFR average to all five published decimal places, using nothing but the raw daily fixings. Calculations follow the ARRC conventions for USD, the Bank of England's SONIA methodology (Act/365 Fixed), the ECB's €STR conventions and the Japanese cross-industry committee's TONA conventions — including lookback with and without observation shift, holiday day-weighting, and end-date-exclusive accrual periods.
Every rate comes from the primary source: NY Fed, Bank of England, ECB, and Bank of Japan. Nothing is estimated, interpolated, or keyed in by hand.
Five places bank interest calculations go wrong
| Day-count basis | Act/360 for SOFR and €STR, Act/365 Fixed for SONIA and TONAR. A basis mix-up changes the charge by ~1.4%. |
| Lookback convention | “Lookback without observation shift” (ARRC syndicated-loan standard) and “with observation shift” (FRN standard) give different results — your facility agreement specifies which applies. |
| Holiday & weekend weighting | Friday fixings carry 3 days; fixings before public holidays carry more. US, UK, euro-area and Japanese calendars all differ. |
| Rounding | Where and when the rate is rounded (and to how many decimals) moves the final figure by a few dollars per million — enough to flag a reconciliation break. |
| Compounded vs simple | Confirm which methodology your facility uses. Over one month on $1m the difference is small (a few dollars) — over a year it is not. |
Your next interest invoice doesn't have to be taken on trust
SOFR · SONIA · €STR · TONAR — compounded in arrears or simple, with a full exportable daily ledger.
Open the calculator →For informational and reconciliation purposes only — not financial, legal, or accounting advice. Figures should be confirmed against your facility agreement.