Carry Trade Calculator

Calculate the interest earned or paid on a carry position, and how far the rate can move before it is wiped out.

A carry position holds one currency and funds it by borrowing another. Interest accrues on the currency held and is charged on the currency borrowed, and the difference between those two rates — the interest rate differential — is what the position earns or pays for simply existing. This Carry Trade Calculator turns that differential into money for a given position size and holding period, and then tells you the currency move that would cancel it.

Formula: carry = notional x (long rate - short rate) x days / 360

Your figures

Position size

In units of the currency you are buying — the base currency when long the pair, the quote currency when short it. One standard lot is 100,000 units.

Exchange rate

Units of the currency you are selling for one unit of the currency you are buying. Used to restate the carry and the position in the currency sold.

Rate on the currency bought

The annual rate your broker credits on the currency you hold long. Negative rates are accepted — several policy rates spent years below zero.

Rate on the currency sold

The annual rate your broker charges on the currency you are short.

Broker's mark-up

In percentage points shaved off the differential, not a percentage of it. Charged whichever way the differential points: it shrinks a credit and enlarges a debit.

Days held

Day count basis

The year length your broker accrues on. Most money-market rates use 360; sterling and a handful of others use 365.

Results

Carry earned

+937.50

90 days at a net +3.750% a year, in the currency bought

Interest differentialRate on the currency bought less the rate on the currency sold, before the broker takes anything.: +4.000%
Broker's mark-upSubtracted from the differential whichever way it points.: 0.250%
Net differentialWhat actually accrues, as an annual rate.: +3.750%
Period as a fraction of a year90 days on a 360-day year.: 0.2500
Differential over the periodThe net annual rate scaled to the days held.: +0.9375%
Carry in the currency bought: +937.50
Carry in the currency soldThe same interest restated at the exchange rate entered.: +1,171.88
Carry per dayIn the currency bought, then the currency sold. This is the accrual rate, not the period total divided by the days held.: +10.42 · +13.02
Carry before the mark-upWhat the raw differential alone would have accrued over the period.: +1,000.00
Cost of the mark-upThe difference between those two figures, in the currency bought.: 62.50
Position value in the currency sold: 125,000.00
Break-even exchange rateThe rate at which a move in the currency exactly offsets the interest accrued.: 1.23828
Move that offsets the carryThe distance from the rate entered to the break-even rate. It does not depend on the size of the position — the notional cancels.: -0.01172 · -0.9375%
Basis usedEvery figure above depends on this. The same rates on the other basis give an answer about 1.4% different.: 90 days on a 360-day year

What this means

A differential of +4.000% less a 0.250% mark-up leaves +3.750% a year, and 90 days on a 360-day year is 0.2500 of that — +0.9375% on the position, or +937.50 in the currency bought and +1,171.88 in the currency sold. The break-even rate of 1.23828 is where a -0.9375% move in the exchange rate cancels that interest exactly, which is the same percentage as the differential accrued: the position size drops out of both sides of the equation.

Every rate, spread and mark-up above is yours to enter. No rate is fetched and no bank's or broker's figure is preset — where a field opens with a number it is a round illustration to overwrite, because the rate that applies to a transaction is the one that account is actually dealt at.
The two currency amounts are shown without a symbol because they are denominated in the currencies traded, not in an account currency. The figure in the currency sold is the figure in the currency bought converted once, at the rate entered.
Interest is netted rather than compounded. A carry position is two simultaneous positions whose notionals are equal by construction at the rate it was opened, so subtracting one rate from the other is exact at that rate.
The break-even move states the size of currency move that offsets the interest. It is arithmetic about the rates entered, not a statement about whether such a move happens: the carry accrues at a known rate, and the exchange rate does not.
Brokers publish a swap or rollover rate rather than the two interest rates. Where they do, that published figure already contains the mark-up, and the swap calculator takes it directly.
Excludes commission, the dealing spread, and any triple-swap convention that charges three nights at once for the weekend.

The link reopens this calculator with the same numbers. Nothing you enter is sent to a server.

Continue with these figures

About the Carry Trade calculation

The second figure is the important one. Carry trade returns are small, steady and known; the exchange rate is large, unsteady and unknown. A differential of three percentage points held for a quarter is worth about 0.75% of the position, and major currencies cover 0.75% in a quiet week. The break-even rate the calculator reports is not a caveat about the arithmetic — it is a description of the trade.

Every input is yours to set: both interest rates, the broker's mark-up on the differential, the day-count basis the year is measured on, the position size and the exchange rate used to restate the interest. Nothing is preset for any broker, because financing terms differ between brokers and between account types at the same broker, and a default here would be a guess dressed as a fact.

The two currency amounts are shown without a symbol, because they are denominated in the currencies being traded rather than in an account currency. The figure in the currency sold is the figure in the currency bought converted once, at the rate you entered.

Carry Trade formula

gross differential = rate on the currency bought − rate on the currency sold
net differential   = gross differential − broker's mark-up
year fraction      = days held ÷ day count
differential over the period = net differential × year fraction

carry (currency bought) = position size × differential over the period ÷ 100
carry (currency sold)   = carry (currency bought) × exchange rate
carry per day           = position size × net differential ÷ 100 ÷ day count

break-even rate = exchange rate × (1 − differential over the period ÷ 100)
break-even move = −(differential over the period)

position size: Units of the currency you are buying — the base currency when you are long the pair, the quote currency when you are short it. One standard lot is 100,000 units.
rate on the currency bought / sold: The annual interest rates your broker credits and charges on the two sides. Negative values are accepted, because several policy rates spent years below zero and a carry calculation that cannot express that cannot describe the trades those rates produced.
broker's mark-up: Percentage points shaved off the differential, not a percentage of it. It is subtracted whichever way the differential points, so it shrinks a credit and enlarges a debit.
day count: The year length interest accrues on: 360 for most money-market conventions, 365 for sterling and a handful of others. The two differ by about 1.4% of the interest.
break-even rate: The exchange rate at which the currency move exactly offsets the interest accrued. It sits below the rate entered when carry is earned and above it when carry is paid.

The two interest rates are netted rather than compounded because a carry position is two simultaneous positions, not a sequence of them. Interest is earned on the currency bought and paid on the currency sold, on notionals that are equal by construction at the rate the position was opened. Subtracting one rate from the other is therefore exact at that rate, which is why the answer is computed in the bought currency first and converted only once at the end, rather than being accrued separately on each leg and reconciled afterwards.

The mark-up is expressed in percentage points rather than as a percentage of the differential because that is how brokers apply it. Half a point taken from a three-point differential leaves two and a half; the same half point added to a differential of minus one leaves minus one and a half. Modelling it as a percentage of the differential would make it vanish as the differential narrows, which is the opposite of what happens — a narrow differential is where the mark-up does the most damage relative to what is left.

The break-even rate collapses to something worth memorising. Setting the currency loss equal to the interest earned gives position size × (rate − break-even rate) = position size × rate × period differential ÷ 100, and both the position size and the rate cancel from that equation. What remains is a percentage move equal to the differential accrued over the period. Carry a three-point differential for ninety days and a 0.75% move against you erases it, regardless of whether the position is a micro lot or fifty million.

It is worth being direct about what that implies. The carry and the currency move are not independent variables that happen to sit in the same equation: the pressures that widen an interest rate differential also move the currency, and carry positions across the market are unwound at the same moments, which is why the adverse move usually arrives as a crowd rather than as a drift. The calculator quantifies the interest exactly and quantifies the move that cancels it exactly. It says nothing about which of the two arrives.

Carry Trade: a worked example

A 250,000-unit long position in a currency paying 4.85% a year, funded by selling one that costs 1.35%, held for 90 days on a 360-day year, with the broker shaving 0.40 percentage points off the differential and an exchange rate of 1.8000 units of the currency sold per unit bought.

Gross differential4.85% − 1.35% = +3.500%
Net differential3.500% − 0.400% = +3.100%
Year fraction90 ÷ 360 = 0.2500
Differential over the period3.100% × 0.2500 = +0.7750%
Carry in the currency bought250,000 × 0.7750 ÷ 100 = +1,937.50
Carry in the currency sold1,937.50 × 1.8000 = +3,487.50
Cost of the mark-up2,187.50 − 1,937.50 = 250.00
Break-even rate1.8000 × (1 − 0.7750 ÷ 100) = 1.78605
Move that offsets the carry1.78605 − 1.8000 = −0.01395, or −0.7750%

The position accrues 1,937.50 units of the currency bought over the quarter, or 3,487.50 in the currency sold, of which 250.00 was handed to the broker as mark-up. The exchange rate only has to fall from 1.8000 to 1.78605 for the currency loss to swallow the lot: 250,000 × 0.01395 is 3,487.50 in the currency sold, which is the carry exactly.

How to use the Carry Trade calculator

Enter the position size in units of the currency you are buying. If you are long a pair that is the base currency; if you are short it, the currency you are buying is the quote currency, so size the position in that instead.
Enter the exchange rate as units of the currency you are selling for one unit of the currency you are buying. It is used only to restate the interest and the notional, so it does not affect the differential or the break-even percentage.
Take both interest rates from your broker's financing schedule rather than from central bank headlines. An interest rate differential calculator is only as good as the two rates it is given, and brokers accrue on their own funding rates, where the gap from the policy rate is often larger than the mark-up.
Enter the mark-up in percentage points, not as a percentage of the differential. If your broker publishes a single swap or rollover figure instead of two rates, that figure already includes their mark-up, so the swap calculator — a rollover interest calculator that starts from the published number — takes it directly.
Match the day count basis to what your broker actually uses. Ninety days on a 360-day year and ninety days on a 365-day year differ by about 1.4% of the interest, which is more than many mark-ups.
Read the break-even move as a percentage rather than as a rate. It does not depend on position size at all, so it is the one figure that transfers unchanged between a demonstration and a real position.

Limitations of the Carry Trade calculator

Every calculation makes assumptions. These are the ones that matter here.

Excludes the dealing spread and any commission. Both are paid up front, and on a short holding period they can exceed the entire carry the position will accrue.
Ignores the triple-swap convention. Most brokers charge or credit three nights of financing on one day of the week to cover the weekend, which changes the daily pattern even though the weekly total is similar.
Assumes the financing rates hold for the whole period. Broker rates are reset frequently and move with policy expectations, so a long holding period is a sequence of different differentials rather than one.
Interest is netted at the opening exchange rate rather than accrued on each leg at the prevailing rate each day. The difference is small for modest rate moves and grows with both the holding period and the size of the currency move.
The break-even rate describes arithmetic, not likelihood. It states the size of the move that cancels the carry; it says nothing about whether such a move occurs, and historically these moves have arrived suddenly rather than gradually.

Frequently asked questions about Carry Trade

Why is the break-even move the same percentage as the differential?

Because the position size cancels from both sides of the equation. The carry is the notional multiplied by the accrued differential, and the currency loss is the notional multiplied by the percentage move, so setting them equal leaves the two percentages equal to each other. That is why the break-even figure is the one number from this calculator that transfers unchanged between a 1,000-unit position and a fifty million unit one.

How is this forex carry calculator different from the swap calculator?

This one starts from two interest rates and a mark-up, which is useful when you are assessing a differential before choosing a broker or comparing what different brokers charge for the same trade. The swap calculator starts from the single rollover figure a broker publishes, which already contains their mark-up. Use whichever matches the numbers actually in front of you.

Does the day count basis really matter?

It changes the interest by about 1.4%, which sounds trivial until you compare it to the differentials being measured. On a 0.5% differential that is a bigger effect than several brokers' entire mark-up. Both 360 and 365 are in everyday use, and the two conventions can even appear on different currencies within the same account, so the basis is asked for rather than assumed and printed back beside the result.

Can the carry be negative on both sides of the trade?

The gross differential cannot be, because reversing the position reverses its sign: if one direction earns 3.5% the other pays 3.5%. The net differential is a different matter. The mark-up is subtracted whichever way the gross points, so 0.40 points charged against a differential of 0.20 leaves −0.20 one way round and −0.60 the other — both sides pay. Entering the mark-up rather than assuming it away is what makes that visible.

What happens if the interest rates go negative?

The calculator accepts negative rates on either side and handles them without special cases, because subtraction does not care about signs. Being long a currency with a rate of minus 0.75% and short one paying 2% gives a differential of minus 2.75%, so the position pays carry in both directions at once. Several major currencies spent years in exactly that position, and a calculator that rejected it could not describe the trades it produced.

Last reviewed 29 August 2026. See our methodology and editorial policy.

More forex calculators