APR math

spread /8h × 3 × 365. A scale for comparison, not a forecast — and the difference matters.

The formula

Everywhere ARBHUB shows an APR, it is the same arithmetic:

• APR = spread per 8h × 3 × 365
• Three 8h windows a day, 365 days. A 0.530% /8h spread reads as 0.530 × 3 × 365 = 580% APR.

No compounding, no reinvestment assumptions, no fee model. It is the current instant’s rate, held flat for a year, stated in annual terms.

What it is for

Comparison across assets on one scale. “0.53% per 8h” and “0.021% per 1h” are hard to rank at a glance; 580% vs 67% is not. APR is the common denominator that makes a thousand rows sortable — that is its entire job.

What it is not

A forecast. Funding is recomputed every interval from live positioning. The rate that annualizes to 580% today can halve at the next settlement or flip sign tomorrow. Real collected yield over a month is a path of hundreds of different prints, not one number times time. The retrospective gap between headline APR and collected funding is usually large.

Meaningful for one-off events. A basis dislocation is a single move, not a repeating payment. Annualizing a 0.8% gap that closes once produces a four-digit percentage with no corresponding cash flow — which is why basis rows in the hero and the matrix show the gap itself, not an APR.

Net of anything. Fees, slippage, adverse entry basis and flips all come out of the gross number. A 40% APR spread with 0.24% round-trip costs and a 4h holding period nets nothing.

Reading APRs sanely

• Treat APR as ranking units. Higher APR = wider current spread. Full stop.
• Ask how long the rate has held. The Spread page’s 7d sign-persistence and stability metrics exist because the same 580% headline means different things on a rate that held for a week vs one printed an hour ago.
• Be suspicious of four-digit APRs. They concentrate in thin books, stale quotes and artifacts — the sanity filter hides most, not all. See Data artifacts.