Funding rate cost calculator — carry on perpetual positions

Funding in perpetual futures is a recurring carry transfer between longs and shorts, designed to keep the contract aligned with the spot market. That mechanism can look minor on a single interval, yet over several days it often becomes one of the most important components of trade economics. In quiet markets especially, the data shows that financing drag can matter more than small price fluctuations, which is why funding deserves to be separated from directional PnL rather than treated as a footnote.

This calculator isolates that carry effect. By translating an 8-hour funding rate into per-period cost, total cost across the holding window, and a simple annualised equivalent, it helps frame the trade as more than a price view. Traders often use that lens when comparing whether to keep exposure in a perpetual contract, move to spot, or consider a dated futures structure. The same logic also works in reverse: funding is not only an expense. When a position is on the side receiving payments, the recurring transfer becomes carry income, which can materially change how a position is interpreted over time.

The calculation starts with notional, meaning the full dollar value of the position rather than the margin posted to support it. Funding is applied to that full exposure, so the payment scales with position size, not collateral. The quoted funding rate is an 8-hour rate, and on major venues funding typically settles three times per day. For each interval, the payment is calculated as notional multiplied by the funding rate. That per-period amount is then repeated across however many funding intervals the position remains open.

To convert holding time into intervals, days held are multiplied by three because each day contains three 8-hour funding windows. Side also matters. For a long position, positive funding represents a payment, while for a short position the sign interpretation flips, so a negative funding rate can still mean the short is paying. The annualised figure is a simple extrapolation of the current 8-hour rate using rate × 3 × 365. It is best read as a standardized estimate for comparison, not as a guaranteed forward funding path.

This calculator is most useful when the holding period extends beyond a few hours and funding has time to accumulate into a meaningful carry component. Before entering a perpetual trade, it helps estimate whether recurring funding is likely to erode the expected edge over the intended time horizon. That matters most when the directional thesis is modest, because even a stable market can still generate a noticeable financing drag through repeated settlements.

It is also relevant when comparing structures. Traders often use it to assess whether keeping exposure in a perpetual contract is materially more expensive than holding spot or using a dated futures contract for a longer-term view. The same framework becomes valuable after a position has already been open for several days, when realized carry may begin to matter more than the precision of the original entry. It can also clarify whether a funding spike is large enough to become part of the thesis for the side receiving payments. By contrast, it is less informative for very short intraday trades where one or even zero funding events are likely to occur before the position is closed.

Consider a trader holding a 10,000 USD long in a perpetual futures contract for 5 days, with funding set at 0.03% every 8 hours. The first step is to convert the funding rate from percent to decimal: 0.03% = 0.0003. Funding is charged on notional, so the per-period payment is 10,000 × 0.0003 = 3 USD for each 8-hour interval.

Next, the holding period is translated into funding events. Five days contains 5 × 3 = 15 funding intervals. Repeating the 3 USD payment across those 15 intervals gives a total funding cost of 3 × 15 = 45 USD. Using the simple annualisation method, the current 8-hour rate converts to roughly 0.03% × 3 × 365 = 32.85% per year. In this scenario, the conclusion is straightforward: a 10,000 USD long held for 5 days at 0.03% funding every 8 hours would pay about 45 USD in total funding, across 15 funding periods, with an annualised carry rate of roughly 32.85%.

A frequent mistake is applying the funding rate to margin instead of notional. Because funding is charged on full position exposure, using posted collateral understates the true carry cost and can make a leveraged position appear cheaper than it really is. Another common error is forgetting that the quoted rate is per 8 hours, not per day. If the holding period spans several days or a week, the rate must be multiplied by the number of funding intervals rather than used only once.

Sign convention also causes confusion. Positive funding does not mean both sides pay; it indicates which side transfers value, and the interpretation changes depending on whether the position is long or short. Traders also sometimes read the annualised figure as a forecast, when it is only a mechanical extrapolation of the current 8-hour rate. Finally, the calculator assumes a constant-rate scenario for the selected period. In practice, funding can change at each interval, so the result is best understood as an estimate based on the current rate rather than a record of what future settlements must be.

Funding cost is closely linked to leverage because recurring payments are charged on notional while traders often think in terms of margin. That means the same funding rate can have a much larger practical impact on equity when leverage is high, even if the position size itself is unchanged. For that reason, funding analysis often sits alongside leverage and margin calculations when traders assess the full economics of a perpetual position.

It also complements liquidation analysis. A market does not need to move sharply for a position to weaken over time; carry drag can steadily reduce account equity even in relatively flat price conditions. In broader derivatives analysis, funding is often compared with the spot-versus-perp basis and with the total PnL outputs shown in leverage PnL calculators. Those tools describe different parts of the same picture: directional gain or loss, financing transfers, and the effect of structure choice on the final result. Looking at them together gives a cleaner view of whether returns are coming from market movement, carry, or both.