A B757 ON INTL OPS FUELED IN KILOS WAS INCORRECTLY FUELED BECAUSE THE LBS CONVERSION WAS INCORRECT. ACFT DIVERTED TO A FOREIGN ARPT FOR EMER FUEL.

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FLT WAS TO OPERATE FROM ZZZZ1 TO ZZZZ2. THE FLT PLAN WAS COMPLETED BY THE COMPANY OWNING THE ACFT. THE FUEL LOAD WAS FIGURED IN KILOS. I WAS TOLD THAT THE ACFT FUEL GAUGES WERE IN KILOS. THE FUEL LOAD CALLED FOR 29500 KILOS. THE FUELER ASKED HOW MANY KILOS YOU WANT LOADED. I SAID TO FILL IT UP. THE FUEL SLIP CAME BACK WITH 53000. SEEMED RIGHT. HOWEVER; WITH THE DIFFERENT FUEL LOAD; THE NUMBERS ON THE FLT PLAN DID NOT MATCH THE GAUGES; SO CONSTANT CONVERSIONS HAD TO BE MADE. APPROX 50% INTO THE FLT WE HAD ALREADY USED 2/3 OF OUR FUEL LOAD AND AT THAT TIME DISCOVERED THAT THE FUEL GAUGES WERE IN LBS AND NOT IN KILOS. NOT ONLY DID WE NOT GET A FULL FUEL LOAD; WE DID NOT EVEN GET OUR PLANNED LOAD. AS A RESULT THE ACFT WAS FORCED TO DIVERT INTO ZZZZ3 FOR FUEL. SUGGEST THAT ALL FIGURES FOR ACFT SHOULD BE IN THE SAME UNITS; EITHER ALL KILOGRAMS OR ALL LBS. PLTS HAVING TO USE A CALCULATOR AT EACH WAYPOINT TO ENTER THE FUEL DIVIDE BY THE APPROPRIATE CONVERSION; CONVERT THE FIGURES ON THE FLT PLAN AND THEN COMPARE; LEAVES TOO MANY PLACES FOR ERRORS ON A 2 MAN CREW.