Conversion factors

Given below are some conversion factors and examples of the necessary calculations.

 Note: If you know one conversion, e.g. 1 foot equals 305mm, then 3.5ft =  3.5 x 305 = 1067.5mm. The converse also applies, i.e. if you have a length of 2010mm then by dividing it by 305mm (that is 305mm per foot) you will find the length in feet:

2010 / 305  ₌  6.59 ft  =  6ft + (0.59 x  12) ins. = 6ft  7.08 ins.      

This applies to all of the conversion factors, e.g. 1sq. ft. = 0.093 sq. m.

Now there is 0.093 sq. m. in 1 ft to find how many sq. ft there are in 1metre,

divide 1 metre by 0.093 i.e.    1 /  0.093    =  10.764 sq ft.                                                  

Calculation examples.

 Linear

1. To convert 3.5 inches to millimetres:  multiply the inches by the number of millimetres in an inch:  3.5 x 25.4 = 88.9 millimetres.
2. To convert 287 mm to inches:  multiply the millimetres by 0.0394: 287 x 0.0394 = 11.31 inches.
3. To convert 4ft 5ins to metres:  (a) multiply the 4ft by the number of millimetres in a foot and (b) the 5 inches by the number of millimetres in an inch and then add the two answers (a) and (b) together:  (a) 4 x 305 = 1220 millimetres, (b) 5 x 25.4 = 127 millimetres, adding the both of them = 1347millimetres. Now divide the answer by 1000 to convert to metres: 1347/1000 = 1.347 metres.
4. To convert 3 yards to metres: multiply 3yds. by 915 millimetres and divide by 1000: 

3 x  915 / 1000 =  2745 / 1000 =  2.745 metres.

5. To convert millimetres or metres to inches or feet or yards, do the same as for the examples above using the correct conversion factors.

Areas

1. To convert an area of 120mm x 50mm to square inches, first multiply the two figures and then muliply by the conversion factor 0.00155:  (a) 120 x 50  =  6000  (b) 6000 x 0.00155  =  9.3 sq. ins.
2. To convert an area of 26.5 sq. ins. to sq. cms., multiply 26.5 sq. ins. by  the conversion factor of 6.4514:   26.5 x 6.4514  =  170.96 sq. cm.
3. To convert an area of 6.3 sq. ft. to sq. metres, multiply 6.3 sq. ft. by  the conversion factor of 0.093:   6.3 x 0.093  =  0.5859 sq. m.
4. To convert an area of 1.78 sq. m. to sq. ft.: multiply 1.78 sq. m. by the conversion factor of 10.764:  1.78 x 10.764  =  19.16 sq. ft

Volume

1. To convert a volume of 189 cu. cm. to cu. ins.: multiply 189 cu. cm. by the conversion factor of  0.061:  189 x 0.061  =  11.529 cu. ins.

2. To convert a volume of 120 cu. ins. to (a) cu. cm. and (b) to cu. m.:

(a) multiply 120 cu. ins. by the conversion factor of  16.387 and

(b) multiply 120 by the conversion factor of 0.000016387: 

(a)  120 x 16.387  =  1966.44 cu. cm. and

(b)  120 x 0.000016387  =  0.00196644 cu. m.

3. To convert a volume of 1.85 cu. m to cu. ft.:

multiply 1.85 cu m. by the conversion factor of 35.316: 

1.85 x 35.316  =  65.335 cu ft.

When buying wood it is often priced in cubic feet, e. g. ash  at  1in by 6in  -  £22.00 per cu. ft.

If you want to buy 25ft of 1in by 6in ash, then you must work out the volume of ash you require by converting all measurements to the same units i.e. all inches or all feet.

If you make all measurements into feet, then multiply:

25 ft x 1/12 ft x 6/12 ft = 25  x 1 x 6 /1 x 12 x12 = 150 / 144   = 1.042 cu. ft..

The cost of the wood will be 1.042 x £22.00  =  £22.95.

If VAT has to be added then the total price will be £22.95 + 17.5%  =  £26.94

If you want to use inches for your measurement, then convert all measurements to inches.

[25ft x 12] x 1in x in = 1800 cu. in., this now has to be converted to cu. ft.. There are 1728 cu. ins. in a cu. ft.,( i.e. 12in x 12in x 12in), therefore dividing 1800 by 1728 will give the volume in cu. ft i.e. 1800/1728  =  1.042cu. ft..

As this volume is the same as the example worked out in cu. ft. the price of the wood will be the same.

Some suppliers quote prices in wood thickness per square metre, e.g.

Mahogany

Price per square metre

21mm          @       £ 39.00

15mm          @       £ 30.90

To calculate the cost of the wood, first find out the thickness you require, let us say 15mm thickness so we know the price per square metre is £30.90.

Now let us assume the width required is 6ins (that is, from the conversion factors above, 6 x 25.4 = 152.4mm = 0.1524m) and the length needed is 11ft.(that is from the conversion factors above 11 x 305mm = 3355mm which is 3.355 metres).

The thickness is known, in this case 15mm, so all that has to be done is to calculate the area required and for this you must multiply the length by the width in metric measurements as the price is in £ per square metre.

Area = length x width = 0.1524 x 3.355 = 0.5113sq. m.

Therefore the cost of the mahogany is £30.90 x 0.5113 = £15.80.

If VAT has to be added, then add on VAT at the standard rate of 17.5%, which is £2.77.

The total then is £15.80 + £2.77 = £18.57.

this article was written for this web site by D Aldridge.