Metric system has came in existence and now the system international units have become much popular .Tt is arithmetic friendly as the calculations are easy. It is friendly with decimal system. The terminology is also easy to remember there is uniformity in it and in naming the fundamental units also. We can see that there is certain easy way it sounds when we say a kilometre or a kilogram. A kilogram is 1000 gram , a kilometer is 1000 meter and therefore, without strain to mind we can conclude that a one thousand litre can be called a kilolitre. Despite some variations in metric system over time, it is easy to adopt it.Just look at one example how the length is measured in both systems.Kilometer =1000 metres,Hecto meter =100 met, Deca met = 10 met , decimetr =0.1 met , centimeter =1/100 meter. The conversion here is easy as it goes in ten's power with our popular decimal system. In British system these day today using measurement of length is mile =8 furlong, 1 fulong =220 yards, 1yard =3 feet , 1 feet =12 inches. The naming of the different units difficult remember. Conversion of 1 unit to another unit require invariably difficult as you have remember the chart or keep the chart before you. Similar is the difficulty in case of other fundamental units.
The main advantage of metric system is derived from the fact that it is based on a decimal system, which is also the system we use for counting and all our calculations in normal life. This makes it easier for common people to make calculations they are required to make in their daily transactions such as buying selling and other calculations involving quantities and costs. This is the only reason why many countries have officially changed over to the metric system from other prevalent systems.
Once metric system has been made an internationally accepted standard system it also offers the advantage of being compatible with measurement and currency system followed in many different countries.
By the way it is worthwhile noting that British System is no longer the standard measurement system used in Britain.