π Forward Rate Calculator
Fair forwards from interest parity.
Fair forward exchange rate
Estimates for planning only, not financial advice.
The fair forward rate comes from covered interest rate parity: spot times the ratio of the two money-market growth factors. With spot at 1.0800, a 4.50% domestic rate, a 2.00% foreign rate, and 90 days, the fair 90-day forward is 1.08 x (1 + 0.045 x 0.25) / (1 + 0.02 x 0.25) = 1.0867. Any market quote far from this is an arbitrage waiting to happen.
How to Use This Calculator
Enter the spot rate, the domestic and foreign interest rates for the tenor, and the days to settlement. The calculator returns the no-arbitrage forward rate.
Enter the spot rate in direct quotation (domestic per foreign).
Enter both interest rates as annual percents for the period.
Read the fair forward. To check a live dealer quote against it, use our interest rate parity calculator.
The Forward Rate Formula
The logic is airtight under its assumptions: borrow domestic, convert at spot, invest foreign, and sell the proceeds forward. If the forward differed from this price, the round trip would print risk-free money, so competition forces it into line. The formula uses simple interest with a 360-day year, the money-market convention for most pairs. For tenors beyond a year, compounding replaces the simple factors, but the principle is identical.
Worked Example
Spot 1.0800, domestic 4.50%, foreign 2.00%, 90 days. Domestic factor: 1 + 0.045 x 90/360 = 1.01125. Foreign factor: 1 + 0.02 x 90/360 = 1.005. Forward = 1.08 x 1.01125 / 1.005 = 1.0867. The 67-pip premium reflects the 2.5-point rate gap over a quarter year. Flip the rates, domestic 2% and foreign 4.5%, and the forward drops to about 1.0733, a discount, because now the foreign currency carries the higher yield.
When Parity Breaks
In calm markets with free capital flows, deviations are tiny and fleeting. They widen when they should not be arbitraged away: during crises when balance sheets are constrained, under capital controls, or where credit risk differs between the two funding markets. The persistent post-2008 cross-currency basis is the famous example: dollar funding commanded a premium that parity said should not exist, and it persisted because regulation made arbitrage balance-sheet expensive.
My take: compute the fair forward first, then ask why the market differs before trading the gap. Nine times out of ten the gap is your error: wrong day-count, mismatched tenors, or a rate from the wrong market. The tenth time, size it small, because parity violations can persist longer than your funding lasts.
Estimates for planning only, not financial advice.
Frequently Asked Questions
How do you calculate a forward exchange rate?
Multiply spot by the ratio of growth factors: F = S x (1 + rd x t) / (1 + rf x t), with simple interest and a 360-day year for standard tenors. That is covered interest rate parity, the no-arbitrage forward price.
What is covered interest rate parity?
The principle that the forward rate must offset the interest differential between two currencies, or risk-free arbitrage exists. Borrow one currency, invest in the other, hedge with the forward: the round trip should earn zero.
Why 360 days in the formula?
Money-market convention for most currency pairs uses a 360-day year. Sterling crosses often use 365. The difference is minor but real, so match the convention of the pair you trade.
Do I need compounding for long forwards?
Beyond one year, markets compound the factors instead of using simple interest. The calculator's simple-interest form is standard for tenors under a year, where the difference is negligible.
What moves forward rates day to day?
Spot moves and interest rate expectations. A rate-hike repricing in either country shifts the forward even if spot sits still, which is why forwards twitch around central bank meetings.
Is the forward rate a forecast?
No. It is an arbitrage price derived from interest differentials, not a prediction of future spot. Research consistently finds forwards forecast poorly; treat them as hedging prices, not views.
What is the difference between outright and swap points?
The outright is the full forward price; swap points are the forward-minus-spot difference quoted in pips. Dealers quote points, clients often think in outrights. This calculator gives the outright.
Can retail traders use forwards?
Mostly through rolling spot or CFDs rather than deliverable forwards, which are institutional and OTC. The parity math still governs the pricing you see, including the overnight financing on leveraged positions.
What is an NDF?
A non-deliverable forward, cash-settled in a convertible currency, used where the underlying currency cannot be delivered offshore. NDF-implied rates often diverge from onshore forwards under capital controls.
How do swap points relate to the outright?
Add the swap points, quoted in pips, to spot to get the outright forward. Dealers quote points because they move less than the outright; this calculator works backwards from the outright you care about.