We all (or most of us here) like to think metric but are having to put up with those wretched non-metric units that plague us in everyday life. Well I've a few methods that in some cases can make it a little easier to convert mentally.
1 in = 2.5 cm (exact conversion 1 in = 2.54 cm) Multiply by 10 and divide by 4, or halve and halve again, example: 18 in (x 10) --> 180 (halve it) --> 90 (halve it again) --> 45 cm 1 ft = 0.3 m (exact conversion 1 ft = 0.3048 m) multiply by 3 and divide by 10, example 50 ft (x 3) --> 150 (div by 10) --> 15 m 1 yd = 0.9 m (exact conversion 1 yd = 0.9144 m) Reduce by 10 %, example 200 yd (subtract 10% of 200) --> 180 m 1 mile = 1.6 km (exact conversion 1 mile = 1.609 344 km) Multiply by 3, halve it and add 10% of the original, example 500 mile (x 3) --> 1500 (halve it) --> 750 (add 10% of 500) --> 800 km 1 lb = 0.45 kg (exact conversion 1 lb = 0.453 592 37 kg) Halve it and reduce by 10%, example 180 lb (halve it) --> 90 (subtract 10%) --> 81 kg Please note one thing though. If you are converting from what is originally only a rough approximate measurement try to reflect that in the result. For example, in the US it seems to be commonly assumed that someone of average height and weight is 180 lb. The above example shows this converts to 81 kg, but since the estimate is unlikely to be accurate to the nearest lb or even 2 lb, it would be better to regard the equivalent as 80 kg (nearest 5 kg say). Hope that's useful. Phil Hall > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > Behalf Of Gavin Young - Renewable Electricity Solutions > Sent: 03 March 2005 02:46 > To: U.S. Metric Association > Subject: [USMA:32342] Re: Conversion > > > A way that a quick mental calculation estimate could have been done is to > remember that a meter is a little longer than a yard, and thus a little > longer than 3 feet. Thus a square meter would be a little more > than 9 square > feet. One square foot is thus about 1/9 th of a square meter, thus, one > square foot equals about 0.1 square meters. > > ----- Original Message ----- > From: "David King" <[EMAIL PROTECTED]> > To: "U.S. Metric Association" <[email protected]> > Sent: Wednesday, 02 March, 2005 03:46 > Subject: [USMA:32337] Re: Conversion > > > > I meant 0.0929 not 0.929, got fooled by the erroneous conversion factors > > you were given by others. > > > > Anyway, 0.0929 is close enough to 0.1, making it easy to remember that a > > value in square feet is about 10 times the value in square metres, thus > > if the difference is quite different to a factor of 10 then something is > > wrong, i.e. some lesser educated mortals try to do a linear conversion > > for area, so they get 1 square foot = 0.3048 square metre > > > > David King
