How do you calculate a volume of a cube in ltrs?

If you convert the dimensions to meters, then when you calculate volume, you will get m3. Then use the conversion factor 1 m3 = 1000 L, so multiply by 1000 (L/m3). Or you can take the measurement in centimeters, then 1 cm3 = 1 mL = 0.001 L, so multiply by 0.001 (L/cm3).