What is 210 mm in cm? Prealgebra Ratios, Proportions, Units and Rates Metric System Unit Conversion 1 Answer EZ as pi Aug 15, 2016 210mm div 10 = 21cm Explanation: 10mm = 1cm Changing to a bigger unit the number gets smaller. 210mm div 10 = 21cm Answer link Related questions Which one is greater 5000cm. or 5 meters? How many yards in a mile? Why is the metric system important? What is the metric system? How do you remember the metric system? How does the metric system work? How was the metric system developed? What is the conversions of grams to mL? How many ml is in 2 liters? How do you convert 1.5 kg/L to g/mL? See all questions in Metric System Unit Conversion Impact of this question 14510 views around the world You can reuse this answer Creative Commons License