What Is a Currency Peg? How Pegged Exchange Rates Work

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A currency peg is an exchange rate policy in which a government or central bank fixes the value of its currency to another currency, a basket of currencies or a commodity such as gold, and commits to defend that rate. Under a dollar peg, one US dollar always buys a set amount of the local currency, or stays within a narrow band around it. Officials, not the market, hold the rate there by buying and selling currency, adjusting interest rates and sometimes restricting capital flows.

What Is a Currency Peg?

Under a floating exchange rate, the market sets the price of a currency. Under a pegged system, the government announces a target, called the parity or central rate, and keeps the market price at or near it.

The anchor is usually a currency widely used in trade and finance. The US dollar is the most common because it is the world’s main reserve currency and oil and many other commodities are priced in it. The euro anchors several European and African currencies. Under the Bretton Woods system (1944 to 1971), the dollar was convertible to gold at $35 per ounce, and other major currencies were pegged to the dollar.

The parity need not be one to one. Ratios of 2 to 1, 3.75 to 1 or 102 to 1 all work, as long as the ratio is held steady.

How a Currency Peg Works

A central bank defends a peg the same way any market price is supported: by standing ready to trade at that price.

• When the local currency weakens below the peg, the central bank sells foreign reserves and buys its own currency, shrinking its supply and pushing the price back up. It may also raise interest rates to make holding the currency more attractive.
• When the local currency strengthens above the peg, it does the opposite: it creates and sells local currency and buys foreign currency, adding to its reserves.

Defending against weakness has a hard limit: the central bank can only sell the reserves it has. Defending against strength is limited mainly by the side effects, because printing local currency to buy foreign assets can expand the money supply and push up domestic inflation.

Because a peg ties the two currencies together, the pegging country’s interest rates have to track the anchor’s. If they drift too far apart, investors move money to whichever side pays more, putting pressure on the peg. Hong Kong rates broadly follow US rates because its Linked Exchange Rate System holds the Hong Kong dollar between 7.75 and 7.85 per US dollar.

Calculating Currency Peg

1. The band around a central rate. Many pegs allow a margin of movement:

Upper limit = central rate × (1 + band %) Lower limit = central rate × (1 − band %)

Hypothetical example: a currency is pegged at 5.00 per US dollar with a ±2% band. The upper limit is 5.00 × 1.02 = 5.10 and the lower limit is 5.00 × 0.98 = 4.90. The central bank intervenes if the market rate approaches either edge.

2. Cross rates between two currencies pegged to the same anchor. If both are fixed to the dollar, their rate against each other is fixed as well:

Currency A per Currency B = (A per USD) ÷ (B per USD)

Using the official parities of the UAE dirham (3.6725 per USD) and the Saudi riyal (3.75 per USD): 3.6725 ÷ 3.75 ≈ 0.9793 dirhams per riyal. While both pegs hold, this cross rate barely moves, and a quoted rate that drifts from it tends to attract arbitrage trades.

Interpreting a Currency Peg

A stable price on a chart does not mean the peg is under no pressure. The signs of pressure usually appear elsewhere first:

• Position within the band. A currency sitting at the weak edge for long periods signals steady selling that the central bank is absorbing.
• Reserve changes. Falling reserves mean the bank is spending money to hold the rate.
• Interest rate gaps. Local rates rising well above the anchor’s suggest the bank is paying investors to keep holding the currency.
• Forward rates. If forward contracts price the currency well below the spot peg, the market is pricing a chance of devaluation.

Why Is a Currency Peg Important?

For importers and exporters, exchange rate swings are a cost: a sharp move in a floating currency can wipe out the profit when money is converted back into dollars. With a credible peg, that risk largely disappears against the anchor, and businesses spend less on hedging.

Countries peg for several reasons:

• Trade stability. Economies that depend heavily on trade or a single partner benefit from predictable prices. Aruba, Barbados and Bermuda peg to the dollar partly because tourism revenue arrives in dollars.
• Commodity revenue. Gulf oil exporters earn dollars, so a dollar peg aligns their currency with their main income.
• Imported credibility. A country with a history of high inflation can borrow the anchor central bank’s track record. Argentina’s currency board, which held the peso at one per dollar from 1991, was introduced to end hyperinflation.
• Investment. Predictable exchange rates make long-term foreign investment easier to plan.
• Export pricing. A low peg keeps exports cheap abroad, which can spark trade disputes.

Example of a Currency Peg

Real-world pegs. The Saudi riyal has been fixed at 3.75 per US dollar since 1986, and the UAE dirham at 3.6725 since 1997. The Belize dollar is held at 2 per US dollar. Panama’s balboa is set at par with the dollar, and the US dollar itself circulates as Panama’s paper money. In Europe, the Danish krone sits in ERM II with a central rate of 7.46038 kroner per euro and a ±2.25% band. The CFA franc used in West and Central Africa is pegged to the euro.

China. The yuan was held at roughly 8.28 per dollar from the late 1990s until July 2005. After pressure from major trading partners, China moved to a managed arrangement referenced to a basket of currencies that includes the dollar. The People’s Bank of China sets a daily reference rate and limits how far trading can move from it, which makes this a managed float, not a strict peg.

Hypothetical defense. Suppose a country pegs its currency at 10 per dollar and holds $40 billion in reserves. Investors start selling, and the bank spends $5 billion a month buying the currency back, enough for eight months at that pace. It can raise interest rates to slow the outflow at a cost to borrowers and growth, or let the currency fall to a new rate. That choice is the core trade-off of every peg.

Limitations of a Currency Peg

Loss of monetary independence. A country that pegs its currency and allows free capital flows cannot also run its own interest rate policy, which economists call the impossible trinity. When the anchor country raises rates during a boom, the pegging country usually follows, even if its own economy is slowing.

A peg set too high. An overvalued currency makes imports cheap and exports expensive, causing persistent trade deficits and steady selling pressure. The central bank spends reserves until it runs short or decides the cost is too high. When the peg breaks, the currency can fall sharply: imports and foreign-currency debts cost more in local terms, inflation rises, debt repayment gets harder, and anchor-country investors holding the currency lose value. Examples include the United Kingdom’s exit from the European Exchange Rate Mechanism in September 1992, Thailand’s float of the baht in July 1997 at the start of the Asian financial crisis, and the end of Argentina’s convertibility regime in 2002.

A peg set too low. An undervalued currency helps exporters but raises the cost of imported food and fuel for households, reducing their purchasing power. It also invites accusations of unfair competition from trading partners.

Speculative attacks. A peg is a public promise with a known price. If traders believe reserves are insufficient, they can bet against the currency in size, and their selling accelerates the drain.

Abrupt exits. Pegs can end in a single session, with prices gapping to a new level and little trading in between. When the Swiss National Bank dropped its 1.20 per euro minimum for the franc on January 15, 2015, the franc jumped sharply within minutes. Liquidity disappeared, so some stop-loss orders filled far from their trigger prices, and leveraged accounts faced a margin call or forced liquidation before traders could act.

Soft Peg vs. Hard Peg and Related Terms

• Soft peg. The rate is fixed or managed but adjustable. This includes conventional pegs with a band, crawling pegs that reset the parity in small steps over time, and basket pegs.
• Managed float. The market largely sets the rate, and the central bank intervenes to smooth or steer it. Some sources loosely call this a “managed peg,” but there is no fixed parity.
• Hard peg. A commitment designed to be very difficult to reverse. A currency board must back every unit of local money it issues with anchor-currency reserves at the fixed rate. Hong Kong operates one, and Argentina ran one from 1991 to 2002.
• Dollarization (or euroization). The country stops issuing its own currency and uses another’s, as Ecuador (since 2000), El Salvador (since 2001), Timor-Leste and the Turks and Caicos Islands do with the US dollar. The euro area is a currency union, not a peg.
• Pegging in options markets. An unrelated use of the word: trading an underlying asset to hold its price near an option strike before expiration.

FAQs

The Bottom Line

Importers, exporters, investors and forex traders dealing in pegged currencies face little exchange rate risk against the anchor while the peg holds credibly. The protection depends on reserves, interest rate discipline and political will, and falling reserves, widening rate gaps and weak forward prices often warn of trouble first. When a peg breaks, prices can gap in minutes, so leveraged positions carry risk that a flat chart hides.