737-800 fuel burn is around 46 kg per minute plus 200ish for taxi and another 300 for the approach. Medium weighs; maybe a couple kg/minute more at heavy weights.
That's 2760kg per hour, a lot more than a 737-800 burns. 2200-2400 in the cruise. 5.5kg/air nautical mile.
Looking a SYD-MEL flight today, close to full, burn is 3120 kg, plus 250 APU and taxi. MEL-SYD is a little less with tailwind. 2810 plus 220 taxi/APU.