How cost moves your break even

The debit that exists before anything moves 

A long transacts at the ask and is valued against the bid. A short transacts at the bid and is valued against the ask. Every position is therefore marked against the far side of the quote from the one it dealt on, which means it reports a loss of exactly the spread from the instant it exists. Nothing has gone wrong and no move has occurred. The position is simply being valued at the price it would close at rather than the price it opened at.

Where the pricing arrangement charges commission, the entry side of it is booked at the same moment, as a separate debit rather than inside the price, and the closing side is booked when the position closes. The two together are what the previous lesson assembled into a round turn: the spread met once on the way in and once on the way out, and commission charged on each side.

So the entry price is not the level at which the position is even. Break even is the level at which the value of the position has recovered the whole cost of the round turn, and it sits away from the entry price by a distance that the cost fixes. That distance is the subject of this lesson, and it is worth naming precisely, because it is measured in the instrument's own increment rather than in money.

Turning a cost into a distance 

The conversion is a single division. The cost of the round turn, stated in the account currency, is divided by the money value of one increment of price movement at the size dealt. The result is the number of increments the price has to travel for the position's value to reach zero. For a currency pair the increment is the pip and the denominator is the pip value; for an index contract it is the money amount per index point; for a shares contract it is the money value of the smallest increment the listing quotes in.

Both parts of that division are known at the moment of dealing. The numerator is the arrangement's own published terms. At YAL the typical EUR/USD spread on the Raw Spread account is 0.1 pips, with a commission of $3.50 per lot, per side. The examples below use round assumed figures instead, so the arithmetic stays legible and belongs to no particular arrangement.

Half the distance in that calculation came from the spread and half from the commission, which is a property of the assumptions rather than a general rule. What is general is that both components were determined at the moment of dealing. Neither depends on what the price does next, so the distance can be stated before the position has any result at all.

Direction changes the price, not the distance 

The break even price differs between the two directions, and it has to. A long recovers its cost as the quote rises, so its break even sits above the entry. A short recovers its cost as the quote falls, so its break even sits below. The distance between the entry and that level, however, is identical, because both positions met the same spread on the same quote and were charged the same commission on the same size.

Break even distance is therefore a property of the instrument, the pricing arrangement and the size dealt, and not of the view the position expresses. It is one of the few numbers in trading that is fully determined at the outset, which is why practitioners tend to reach for it when they compare instruments or arrangements against one another.

Size moves the money, and usually not the distance 

Doubling the size doubles the cost of the round turn, which suggests the distance doubles with it. It does not, because doubling the size doubles the value of one pip in exactly the same proportion. A cost that scales with size sits in the numerator, and the size scales the denominator identically, so the two cancel and the distance is unchanged. That is why break even distance can be quoted per instrument at all, rather than having to be recomputed for every size.

The exceptions are costs that do not scale. A flat charge per ticket, a stated minimum commission, or any fixed component of a conversion charge stays the same size whatever the position size is, while the denominator keeps growing. A fixed cost therefore lands on a small position as a large distance and on a larger one as a small distance, which is the arithmetic behind the observation that fixed charges bear unevenly across position sizes.

Every night moves it again 

Spread and commission are settled at dealing and never change afterwards. Financing is different in kind, because it is applied per night for as long as the position remains open. Each application is a money amount, and each converts into distance by the same division: the night's amount divided by the value of one pip at the size held. A debit adds that distance to the break even, moving it further from the current price. A credit subtracts it, moving the break even closer.

This is the mechanism by which the holding period enters a cost calculation that otherwise looks fixed. The break even of a position held across a week is not the break even it opened with, and the difference is not an estimate: it is the sum of the nights that have actually been applied. As the earlier lessons set out, the sign of the adjustment follows the instrument and the direction, one weekday conventionally carries three nights to account for weekend settlement, and the rate is set per night rather than fixed in advance.

Why the distance weighs most over short horizons 

The costs settled at dealing are the same size whether a position lasts a minute or a month. What changes with elapsed time is the range the price has covered. Market convention holds that the distance a price travels tends to widen the longer the window observed, which is why volatility is quoted per period rather than as a single number, and it is the reason a fixed cost is a larger fraction of a short window than of a long one.

Financing runs the other way. It is absent from a position closed the same day and accumulates on one held for weeks, so the component of cost that dominates over a short horizon is the one settled at dealing, and the component that dominates over a long one is the one applied per night. The two effects are in opposition, which is exactly why this arithmetic names no preferable holding period. It states which cost is doing the work at which horizon, and stops there. Which horizon suits any particular set of circumstances is not something a page can assess.

Where practitioners disagree 

The first disagreement is about what belongs in the numerator. One convention counts only what is settled at dealing, spread and commission, which yields a single fixed number per instrument and size that can be checked against the contract specifications. Another adds an allowance for slippage and an estimate of financing, on the reasoning that a distance excluding them understates the cost of any position actually held. The limit of the first is that it is knowably wrong for anything held overnight. The limit of the second is that it presents estimates with the same precision as settled figures, and a number built partly of guesses reads as though all of it were measured.

The second disagreement is about whether break even belongs on a chart at all. Some traditions mark the level and treat it as a reference point. Critics of the practice observe that the level is a property of one account rather than of the instrument, that no other participant can see it, and that reacting to it converts a measurement of cost into a decision rule derived from one's own entry price rather than from anything the market is doing. Neither position resolves the other, and the disagreement is worth knowing about because the same number is being used for two different purposes: as a cost measurement, which it certainly is, and as a level, which is a claim it does not support on its own.