One of the problems encountered by participants in the financial futures markets is determining the quantity of cash they will need to cover marking-to market, or resettlement, requirements. The authors provide a model that allows the prospective hedger (or speculator) to calculate the amount of liquidity needed and the of exhausting this liquidity within a given time period. In general, the size of the liquidity pool, in the case of a single hedge, will depend on four factors-the length of time the position is to be held, the number of contracts traded, the volatility of the futures contract being traded, and the investor's acceptable probability of ruin -that is, of exhausting the liquidity pool. The calculations require only one value to be estimated from the data-the daily standard deviation of the futures price changes, in dollars. For a given liquidity pool, the of ruin increases with the length of the hedging horizon. Probability of ruin also varies significantly with the maturity of the contract being traded;for agiven hedging horizon and liquidity pool, the of ruin is substantially higher with the nearby contract than with the distant contract.