Normalize the two intervals before comparing rates
For long notional L, long rate rL and interval hL hours, the daily funding contribution is −L × rL × 24 ÷ hL. For short notional S, short rate rS and interval hS, it is S × rS × 24 ÷ hS. Add the two signed contributions to obtain the modeled daily total.
This signed formula handles negative funding without a separate rule. A negative long-side rate creates a modeled receipt; a negative short-side rate creates a modeled payment. Comparing the raw displayed percentages before adjusting the intervals can select the more expensive combination.
Model a two-venue position as two independent obligations
Each exchange settles its own contract and requires its own available margin. A gain on one venue may not automatically be usable to support a losing position on the other. Capital allocated to both legs and additional available balances matter when assessing the arrangement.
Use matching underlying assets and understand the settlement currency and contract type. This tool models linear funding cash flows in a common quote unit. It does not normalize inverse contracts, collateral exchange rates, contract multipliers or differences in price indices automatically.
Evaluate net carry alongside basis movement
The holding-period projection applies the normalized daily funding total across the number of days and subtracts the costs entered. It assumes both rates and notionals stay constant. Actual settlement timing can cause individual cash flows to arrive at different times even when the daily totals look balanced.
The price difference between the two perpetual contracts can also widen or narrow. Funding income does not offset every possible change in that spread. This calculator isolates funding and costs; it does not forecast basis movement, coordinate orders or ensure that funds can move between venues when needed.
Questions about this tool
Can both legs receive funding at the same time?
In the modeled convention, yes: a negative rate on the long leg produces a receipt and a positive rate on the short leg also produces a receipt. Whether that combination is available and persists requires current venue data.
Why does the lower displayed rate sometimes produce the higher daily cost?
A rate charged more frequently can accumulate into a larger daily amount. Convert each rate with its own settlement interval before comparing the long-side cost with the short-side receipt.