Currency Forward Rate Calculator
From the spot rate and two interest rates, compute the forward rate (covered interest parity, with days): F = S x (1 + r_f·T) / (1 + r_d·T), T = days/360.
輸入資料
計算結果
重點速覽：Forward rate F = S x (1 + r_f·T) / (1 + r_d·T), T = days/360, quote = local per foreign. It is the no-arbitrage price locked today for future delivery, set by covered interest parity. The higher-rate currency tends to be forward-discounted to offset its interest advantage. WARNING: Real quotes add spreads, day-count (360/365) and costs; education only, not a forecast.
計算公式
F = 即期匯率 ×(1 + 外幣利率 × T) ÷ (1 + 本幣利率 × T)。
T = 天數 ÷ 360。利率高的貨幣遠期通常呈折價。
$$遠期匯率：$F = S\times\dfrac{1+r_f\,T}{1+r_d\,T}$$$$$其中 $S$ 為即期匯率、$r_f$ 為外幣利率、$r_d$ 為本幣利率、$T=\dfrac{\text{天數}}{360}$。$$$$示例 (即期 8、本幣 5%、外幣 2%、360 天)：$8\times\frac{1.02}{1.05}\approx7.7714$$$使用說明
- Enter the spot rate (local per foreign).
- Enter the domestic and foreign annual rates.
- Enter the days to view the forward rate.
即期匯率 8、本幣利率 5%、外幣利率 2% 下的遠期匯率
| 天數 (T) | 遠期匯率 | 相對即期 | 說明 |
|---|---|---|---|
| 360 天 (1) | 7.7714 | 低於即期 8 | 本幣利率高 → 遠期折價 |
| 180 天 (0.5) | 7.8829 | 低於即期 8 | 折價幅度較小 |
| 外幣利率較高之例 | — | — | 見案例二 (遠期升水) |
理財情境案例
案例一：本幣利率較高時的遠期折價
即期匯率 8 (1 外幣 = 8 本幣),本幣利率 5%、外幣利率 2%,期限 360 天 (T = 1)。
遠期匯率 F = 8 × (1 + 0.02×1) ÷ (1 + 0.05×1) = 8 × 1.02 ÷ 1.05 ≈ 7.7714。
解讀：360 天的遠期匯率約 7.77，低於即期的 8——外幣相對本幣『遠期貶值』(折價)。原因是本幣利率 (5%) 高於外幣 (2%),持有本幣能多賺 3% 利息，為了不讓人靠『借外幣、換本幣、賺利差、到期換回』無風險套利，遠期匯率必須讓外幣升值／本幣貶值來抵消利差。這就是利率平價。
案例二：外幣利率較高時的遠期升水
即期匯率 7.8，本幣利率 4.5%、外幣利率 5%,期限 360 天 (T = 1)。
遠期匯率 F = 7.8 × (1 + 0.05×1) ÷ (1 + 0.045×1) = 7.8 × 1.05 ÷ 1.045 ≈ 7.8373。
解讀：這次外幣利率 (5%) 高於本幣 (4.5%),遠期匯率 (7.84) 反而高於即期 (7.8),即外幣『遠期升值』(升水)。方向剛好與案例一相反，因為現在是外幣利息較高，遠期要讓外幣貶值才能抵消——等一下，這裡數字上外幣遠期升值？關鍵在匯率報價方向：這裡 F 上升代表『1 外幣換到更多本幣』,反映的是本幣為抵消其較低利率而遠期貶值。核心原則不變：利率較高的一方，其貨幣在遠期會相對貶值以維持無套利。⚠️ 本計算器採簡單利率、360 天慣例，僅供教學與估算；實際遠期合約的定價、天數慣例與報價方向以交易對手為準，不構成交易建議。
常見問題
What is a forward rate and its relation to spot?
A forward rate is the exchange rate agreed today but settled on a future date, versus the spot rate (immediate settlement). Their gap is set by the interest-rate differential via covered interest parity: F = S x (1 + r_f·T) / (1 + r_d·T). This is a no-arbitrage price, not a market forecast of the future spot.
Why is the higher-rate currency often forward-discounted?
No-arbitrage again. If domestic rates exceed foreign, holding domestic earns more interest; to prevent risk-free 'borrow foreign, convert, earn domestic, convert back' arbitrage, the forward must make the domestic currency appreciate (the foreign currency depreciate) by roughly the rate gap. So the high-rate currency shows a forward discount. This also warns that carry-trade interest gains are often eroded by adverse FX moves.
What are forward contracts used for?
Their core use is hedging FX risk — locking the future exchange rate to remove uncertainty. Importers lock costs (pay foreign later), exporters lock revenues (receive foreign later), investors hedge overseas-asset principal. Hedging cuts bad moves but also forgoes good ones. Note the direction of the quote when interpreting premium/discount.
Can the forward rate predict the future spot?
No. The forward rate is a no-arbitrage price derived from today's spot and rate differential, not a prediction of where spot will be. On delivery day, actual spot is usually different, driven by data, policy, geopolitics and sentiment. Use forwards to lock price and hedge, not as a crystal ball.
Who actually uses forward contracts?
Mainly those with certain future FX flows who want to avoid rate risk: importers/exporters (lock payable/receivable rates), multinationals (repatriate profits), institutions with foreign debt/investments (hedge principal/interest), and investors/funds (currency-hedged returns). Forwards give certainty at the cost of forgoing favorable moves and carry obligation; options and swaps are alternatives. Consult a bank/licensed professional — this tool only explains pricing.
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參考資料
內容審核：香港計算器財經團隊。計算邏輯與公式參考香港金融管理局（HKMA）及投資者及理財教育委員會（IFEC）之個人理財計算指引，結果僅供參考，實際以相關機構公佈為準。