Move the slider to see how units convert into each other, then take on a quiz that estimates about how big everyday objects are.
Guessing "about this much" without a ruler or a scale is called estimating. The same length can be written in mm, cm, m, or km depending on its size โ different units, same real size. They convert by fixed multiples, like 1cm = 10mm, 1m = 100cm, and 1L = 1000mL.
The trick to estimating well is using something familiar as a reference. Once you know a carton of milk is 200mL, you can guess right away that a 2L bottle holds "about 10 milk cartons' worth." Estimating doesn't have one single right answer โ if your guess is close to the real value, you estimated well.
Move the slider and watch how the units change together, guess about how many cm, mL, or g an everyday object is, then check yourself with the quiz.