Convert units of length, mass and time

The conversion table

For lengths and masses, we use a decimal conversion table, where each column is 10 times the value of the previous one:

km / kg	hm / hg	dam / dag	m / g	dm / dg	cm / cg	mm / mg

Enter one figure per column, aligning with the reference unit (m or g), then read the number by shifting the decimal point.

Step-by-step example

Convert 2.5 km to m:

• 1 km = 1000 m, so 2.5 km = 2.5 × 1000 = 2500 m.

Convert 350 g to kg:

• 1,000 g = 1 kg, so 350 g = 350 / 1,000 = 0.35 kg.

The special case of time

Please note: time does not follow a decimal system! You do not divide by 10, but rather:

Unit	Equivalent
1 min	60 s
1 h	60 min = 3600 s
1 day	24 h

Example: 2 h 15 min in seconds -> (2 × 3600) + (15 × 60) = 7200 + 900 = 8100 s.

A common pitfall to avoid

The most common mistake is to apply the decimal conversion table (used for length and mass) to durations. Many pupils write “1 h = 100 min”, which is incorrect: 1 hour is equal to 60 minutes, not 100. Always check the nature of the quantity before converting.