The rate is small. The APR is not.
Funding is the fee that keeps a perpetual future pinned to spot. It's quoted per window — usually every 8 hours — and the headline number is deliberately tiny: a "normal" rate is around 0.01%. The trap is that it's charged again and again. Three windows a day, every day, is 1,095 charges a year. So 0.01% per window is not 0.01% — it's roughly 10.95% APR. In a hot market the rate can sit at 0.05–0.1% per window for days, which annualizes to 50–110% APR. That's the real carry you're paying to hold the position.
And it's worse with leverage. Funding is charged on your notional — the full position — not on the margin you put up. At 10x your position is ten times your collateral, so a 10.95% APR on notional is about 110% APR on your margin. This is why a quiet, ranging market can still bleed a crowded long to death: nothing happens to the price, but funding quietly compounds against you. Use the real futures profit calculator to fold funding into your actual net, and the funding fee calculator for a single specific window.
The break-even move
The most useful output here is the last one: the price move you need just to cover funding. If holding for a week costs 0.7% of your notional in funding, the price has to move 0.7% in your favour before you've made a single cent — you're starting the trade in a hole. A short paying funding in a falling market is being paid to wait; a long paying funding in a flat market is being taxed to wait. Knowing which side you're on, and the size of the carry, is half of whether a multi-day hold is worth it.
How to use it
1. Pick your side — long or short — so the tool knows whether you pay or receive.
2. Enter the current funding rate per window (your exchange shows it on the contract page) and the window length.
3. Enter your position's notional size and leverage.
4. Set how long you plan to hold. Read the APR, the total cost, and the break-even move.
FAQ
Is the APR compounded? This shows simple (non-compounded) APR — rate per window × windows per year — which is how funding is normally quoted and compared. Actual paid funding compounds slightly if you reinvest, but the simple figure is the honest sticker price.
The rate is negative — do I earn? If you're on the side that receives (short when rate is positive, or long when it's negative), the cost shows as a credit. Persistent negative funding can make a delta-neutral carry trade pay you to hold.
Does funding change? Constantly — it's recalculated every window from the perp-vs-spot gap. Treat this as the cost at the current rate; a spike can double it overnight.