What funding fees actually are
Funding fees are the mechanism Bybit uses to keep the perpetual-futures price tethered to the underlying spot price. Because a perpetual has no expiry, there is no natural arbitrage that pulls perp price back to spot when the two diverge. Instead, every eight hours (or every four on some alts), Bybit looks at the funding rate — a number computed from the recent premium of perp over spot, plus an interest-rate component — and one side of the market pays the other directly, in proportion to their position size. When perp trades above spot, longs pay shorts; when perp trades below spot, shorts pay longs. The size of the payment is your funding rate × your position notional, and it happens at exactly 00:00, 08:00, and 16:00 UTC for top contracts.
For a swing or position trader, this matters far more than most realize. A 0.05% funding rate sounds tiny — it is one twentieth of one percent — but it compounds three times per day. Holding a long through a week of 0.05% funding pays 21 × 0.05% = 1.05% of your position size, off the top, before price moves a single tick. For an account leveraged 10x, that is 10.5% of your initial margin in one week — equivalent to giving up the first 1% of price move in your favor every single time you hold a position for seven days.
Why funding rates spike (and when to watch out)
Funding rates are not constant. They follow market sentiment in lockstep. When BTC is ripping and everyone is long, longs are bidding up the perp above spot, so the funding rate climbs — sometimes to 0.1% or higher per 8h on top contracts, and 0.5%+ on hyped low-cap alts during pump moments. Conversely, in panic selloffs the perp trades below spot, funding goes negative, and shorts pay longs. The implication for trading: the funding rate is itself a sentiment indicator. Extreme positive funding is a sign of crowded longs, and the historical pattern is that extreme funding precedes mean-reversion candles — the same crowd that paid up to maintain the long position is the first to liquidate when price softens.
Funding rates also have a tail-risk dimension. During exchange-wide events — major news, BTC halving narratives, regulatory headlines — funding rates can spike to multi-month extremes on alts in particular. SOL has seen 1%+ per 8h during certain narrative weeks (an annualized rate of over 1,000%). Holding a long through one of those windows is mathematically equivalent to paying margin-loan rates from the 1980s. The annualized-rate output on this page shows the extrapolation if the current rate held for a year. Treat values above ~30% annualized as a serious sentiment warning — they almost never persist, and the unwind is sharp.
Funding for scalpers vs swing traders
If your average hold time is under eight hours, you almost never pay funding. Bybit only charges at the funding timestamp — 00:00, 08:00, 16:00 UTC — so a scalper who opens and closes between those windows pays nothing. Swing traders who hold across funding timestamps pay every single one. This is why scalpers and swing traders have totally different funding-cost economics, and why "trading on Bybit" means very different things depending on hold horizon.
For swing traders, the practical implication is: build funding cost into your expected return. If you expect a trade to move 3% in your favor over five days, and the current funding rate is 0.03% per 8h, you will pay 15 × 0.03% = 0.45% in funding. Your net expectation drops from 3% to 2.55% — a 15% haircut on the trade's expectancy. Compound that across many trades and a winning strategy on paper becomes break-even or losing in practice. We have seen this kill traders who were "right" about every trade but lost money over the year — the funding tax silently ate the edge.
The trade most traders should be doing
High-positive funding paired with a setup that has both directional and mean-reversion structure is a setup that pays you to be patient. A short on a contract paying 0.1% per 8h to longs pays the short 9% annualized in carry alone — which is roughly the long-run equity-market return — before any directional move. Traders who specialize in funding-arbitrage strategies build entire books around exactly this dynamic. For directional swing traders, the simpler lesson is: when funding is extreme positive and you have a bearish thesis, the funding accrual is wind at your back; when funding is extreme positive and you want to go long, you are paying 9% APY headwind to hold the position. Adjust position size accordingly, or wait for funding to normalize before entering.
What this calculator does not capture: funding rate changes during the hold. Bybit recomputes the funding rate continuously based on premium and interest, so the rate you see now may be very different from the rate that prints at the next funding timestamp. The honest answer is: you cannot predict exact funding cost over a multi-day hold without monitoring. What you can do is compute the worst-case under current conditions, factor that into your sizing, and revisit if the rate moves meaningfully against you. PerpLog tracks funding accrual per trade in your synced history — every closed trade in your journal includes its funding cost as a separate column, so you can see which trades silently underperformed because of funding tax rather than price.
Related
- → How Funding Fees Destroy Your Crypto Edge — the long-form essay this calculator was built for.
- → Position Size Calculator (Bybit Perpetuals) — risk-sized contracts for any trade idea.
- → Liquidation Price Calculator (Isolated + Cross) — exact liquidation price including MMR tiers.
- → PerpLog vs Edgewonk — honest comparison for crypto traders.
Want to see funding cost on every closed Bybit trade automatically?
PerpLog syncs your Bybit trade history (read-only API) and breaks out gross PnL, fees, and funding cost separately on every closed trade — so you can spot the trades that "won" on price but lost on funding tax. Free tier, no credit card.