Costs to haul iron ore on Capesize ships, the largest carriers of the commodity, reached the highest in 10 weeks on speculation demand to ship the mineral to China increased.

Daily average rates gained 8.7 percent to $5,433, the highest since Feb. 20, figures from the London-based Baltic Exchange showed today. That’s the biggest single-session increase since March 12, exchange data showed.

The current return is 70 percent of the estimated $7,758 a day that Capesizes need to cover operating expenses before paying for fuel, according to London-based accountant Moore Stephens LLP.

“Low port stockpiles and low iron ore prices have spurred some additional Chinese buying of imported iron ore,” Dominic Meredith Hardy, an analyst at shipbroker Galbraith’s Ltd. in London, said by e-mail. “We’ve seen a number of Capesize iron ore fixtures out of Tubarao in Brazil going to Qingdao in China this week as well as a steady flow from Western Australia. We would expect demand from China to continue as long as prices remain low.”

Iron-ore stocks at Chinese ports were the lowest since Dec. 3, 2010, according to data from Shanghai Steelhome Information, an industry research company. Ore with 62 percent iron content delivered to the Chinese port of Tianjin fell 3.5 percent to $129.40 a dry ton today, the lowest since Dec. 14, a gauge compiled by The Steel Index Ltd. showed.