 The ships had a stowage capacity of 1 @,@ 600 long tons ( 1 @,@ 626 t ) of coal and 3 @,@ 400 long tons ( 3 @,@ 455 t ) of oil , giving them a range of 5 @,@ 500 nautical miles ( 10 @,@ 200 km ; 6 @,@ 300 mi ) at a speed of 16 knots ( 30 km / h ; 18 mph ) . Nagato exceeded her designed speed of 26 @.@ 5 knots ( 49 @.@ 1 km / h ; 30 @.@ 5 mph ) during her sea trials , reaching 26 @.@ 7 knots ( 49 @.@ 4 km / h ; 30 @.@ 7 mph ) at 85 @,@ 500 shp ( 63 @,@ 800 kW ) and Mutsu reached the same speed with 87 @,@ 500 shp ( 65 @,@ 200 kW ) . The US Navy did not learn their actual speed capability until about 1937 ; previously it had believed that the ships were capable of only 23 knots ( 43 km / h ; 26 mph ) . 
