Interest Rate Swap Calculator

The mid swap rate here is built from the same broker source the major terminals use, no licence or free seat required. Pick a tenor and it comes straight off our current SONIA, SOFR or EURIBOR curve: floating payments projected off the forward curve, money values discounted with an annuity bootstrapped from the same data. It doubles as an interest rate swap valuation calculator: the second tab reprices an existing swap at today’s mid. Indicative levels: annual fixed leg, bullet notional, spot start. The app prices the exact trade with full conventions.

As of 14 August 2026, the 5 year SONIA mid is 4.349%. Fixing £10,000,000 for 5 years at mid costs £434,900 a year on the fixed leg, with a PV01 of about £4,418. A quote 15bp over mid is worth roughly £66,277 over the term, and that gap is the bank's margin. Now you can see it. These numbers re-run automatically from each daily curve snapshot.

The swap rate (par rate) is the fixed rate that makes a swap worth zero on day one: the present value of the fixed leg equals the present value of the floating leg, with the floating payments projected off the forward curve and both legs discounted back to today. This calculator reads the current mid par rate for your tenor straight off our curve, so you never have to supply a rate yourself.

Pick an index in the calculator above and it shows the latest published mid for any tenor from 1 to 30 years, with the timestamp of the curve it came from. The public snapshot updates daily; in the app the same rates refresh every 30 seconds. SONIA, SOFR, EURIBOR, €STR, SARON, CORRA, TONA and BBSW are all covered.

Reprice what's left of it at today's market rate. The indicative value is (current mid for the remaining term minus your contract rate) times the annuity factor times the notional, positive for the fixed payer when rates have risen. Use the 'Value an existing swap' tab above: enter your fixed rate and the remaining whole years and it does exactly this. For an audit-ready valuation report or a refinancing breakage number, run the same swap through the app.

No, and that's the point. Banks quote mid plus a margin. Type the rate you were offered into the calculator and it shows the spread to mid in basis points and what that spread is worth in money over the life of the swap. You can't negotiate a number you can't see. If the quote is on an amortising profile, check it against your exact notional schedule in the app.

PV01 is the change in the value of the swap for a one basis point move in rates, the money-terms cousin of duration. Treasurers use it to size rate risk and to translate a quoted spread into money: a 5bp margin on a swap with a PV01 of £4,500 costs about £22,500 in present value. The calculator shows it for every swap it prices, so it doubles as an interest rate swap duration calculator.

The free calculator prices spot-starting bullet swaps with an annual fixed leg. Amortising and custom notional profiles, forward starts, precise day counts, OIS discounting and full cashflow schedules with Excel export are in the BlueGamma Swap Pricer, free for 14 days with no card required.

You can build a swap pricer in Excel: bootstrap a curve, maintain the fixings, and keep it alive forever. A terminal does it properly, if you have a licence and the seat is free. This page covers the other 95% of moments: a credible mid, a sanity check on a quote, or a first-pass MtM, right now. When the answer has to be exact, take the same trade into the BlueGamma Swap Pricer, where curves are live and the pricer handles the conventions for you.

Quotes stream from tier-one inter-dealer brokers and exchanges, the same sources the premium terminals use. We sanity-check every feed before building the curve, and the calculator shows the timestamp of the curve it priced against.