Funding: The Cost of Holding a Perp

A perpetual future has no expiry, so nothing forces its price to converge on spot. The funding rate is the mechanism that does that job instead: a periodic payment between longs and shorts that makes holding the expensive side progressively more costly.

For most traders the funding rate is a line item they notice after the fact. It is quoted as a small percentage, sometimes four decimal places, which makes it look negligible. Multiplied by three payments a day and a leveraged notional, a funding rate is frequently the largest single cost of a position that does not move.

• Funding is a transfer, not a fee. One side of the market pays the other. The venue usually keeps none of it, which is why it does not appear in fee schedules.
• The rate is periodic, so it compounds against you. A rate quoted per interval must be multiplied by the number of intervals you hold, not read as a one-off charge.
• Notional, not margin, is the base. Funding is charged on position size, so leverage multiplies the cost relative to the capital you actually posted.
• You pay only if you hold at the timestamp. Positions opened and closed between funding times incur nothing, which makes holding time a decision rather than a detail.

What a funding rate is actually paying for

It is paying for the difference between the perpetual contract and the spot market. When the perp trades above spot, longs are paying a premium for exposure they could otherwise get by buying the asset, so the rate turns positive and longs pay shorts. When the perp trades below spot, the sign flips.

That is the whole design. The payment is an incentive to take the other side, and its size is set by how far the perp has drifted from the underlying index. A large positive rate is not a signal that the market is right; it is a signal that one side is crowded enough to be charged for it.

Two consequences follow. Funding is a cost of consensus: the more people agree with your position, the more you pay to hold it. And a high rate is self-correcting, because it makes the crowded side expensive enough that some participants close or flip.

How the funding rate is calculated and paid

The mechanics vary by venue, but the shape is consistent, and the details are where most cost estimates go wrong.

The interval is the multiplier

Rates are quoted per funding interval, and intervals commonly run at eight hours, though some venues use one, four or variable windows. An eight-hour interval means three payments a day. A rate of 0.01 percent per interval is 0.03 percent per day, not 0.01 percent per day.

Reading a rate without checking the interval misstates cost by a factor of three or eight — the most common arithmetic error in position costing.

Clamps and caps change the picture

Most venues apply a cap to the funding rate and may combine a premium index with a fixed interest component. In quiet markets the premium is small and the interest component dominates, so a positive rate can persist even when the perp trades near spot.

Caps limit how extreme a rate can get in one interval, but not the total: a capped rate applied for weeks still accumulates.

Who pays whom, and when

Payment occurs at fixed timestamps. If you are long and the rate is positive, you pay; if you are short, you receive. Positions opened after the timestamp and closed before the next incur nothing.

This creates a practical asymmetry: a position held for twenty-three hours across two funding times can cost more than one held for twenty-five hours across one. Duration is not the variable that matters — timestamp exposure is.

Funding converts a directional bet into a bet on direction plus time. Traders who ignore the second term are often right about the market and still down on the position.

Worked example: the cost of holding one week

Take a long position with $10,000 of notional exposure at a funding rate of 0.0100 percent per eight-hour interval, three intervals a day.

Cost per interval is 0.0001 × $10,000 = $1.00. Per day that is 3 × $1.00 = $3.00. Over seven days it is $21.00, which is 0.21 percent of notional.

Annualised, the same rate implies 0.0001 × 3 × 365 = 0.1095, or about 10.95 percent per year. That is the number worth comparing against, because a rate that looks like a rounding error per interval is a double-digit annual cost when it persists.

Now change one input. At 0.0300 percent per interval, cost per interval is $3.00, per day $9.00, per week $63.00, and the annualised figure is about 32.85 percent. The position has not moved and the loss is six times larger, entirely from the rate.

Now add leverage. If the $10,000 notional was opened with $1,000 of margin, the weekly funding at 0.0100 percent is $21.00 against $1,000 of capital — 2.1 percent of margin in a week. To break even on funding alone, the underlying has to appreciate 0.21 percent. At the higher rate, the required move is 0.63 percent per week just to stand still.

Finally, compare against trading costs. Assume 0.05 percent per side for illustration, so a round trip on $10,000 costs $5.00 each way, or $10.00. At the lower rate, a week of funding costs $21.00 — more than double the round-trip fee. Over a month, funding dominates: roughly $90 against $10.

Comparing holding costs across venues

Because intervals and formulas differ, two venues quoting the same-looking rate can charge different amounts for the same position.

The fourth row is the one most often skipped. A rate observed now says little about the average you will pay over a month, because funding responds to positioning and can change sign within days.

When funding becomes the dominant cost

Funding dominates when the position is held long enough and the rate is persistent enough that trading fees stop being the main expense. That condition is common in trending markets, where the crowded side pays continuously.

Short holds versus long holds

For a position held hours, fees and spread usually outweigh funding, and interval timing can avoid payment entirely. For one held weeks, the ranking inverts.

The crowded-side problem

A high positive rate means longs are paying to be long. If your thesis is that the price rises, you are paying for agreement. The position can be correct and still lose money if the move is smaller than the accumulated funding.