 13 May 2021
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Electrical Formulas
 Updated on 13 May 2021
 5 Minutes to read

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Before reading this article, please make sure you are familiar with Measurement  Parts & Labour in Groundplan.
Parts, labour and the formula used are unique to each project and company, the information below details some examples of electrical items being measured on plans and the formulas used to calculate additional parts and labour.

The formula given is a guideline to be used to calculate your own measurement parts and labour.

The formula bar follows the PMDAS Rule: Parentheses first, then Multiplication, Division, Addition & Subtraction, respectively.
Double GPO
When counting double GPO's on a plan there are also other parts and labour you may want to quantify.

Double GPO  to allow one double GPO per count
Formula:
count
Breakdown:
To quantify one part per count, the formula remains simply “count” ascount x 1 = count
. 
Wall bracket  to allow one wall bracket per double GPO counted.
Formula:count

2.5mm twin and earth quantified per m  to allow
12m
of cable per double GPO counted.
UOM:m
Formula:count * 12
Breakdown:
count
 the number of GPOs;
* 12
 to allow for 12 meters of cable per count. 
2.5mm twin and earth from a 100m cable drum  to allow
12m
of cable per double GPO counted when you purchase cable in100m
cable drum.
UOM:Drum
Formula:count * 12 / 100
Breakdown:
count
 the number of GPOs;
* 12
 to allow for 12 meters of cable per count;
/ 100
 to get the proportion of the drum the cable is purchased in. 
2.5mm Cable Clips from a 500 jar to allow
5
cable clips per double GPO counted when you purchase cable clips in a jars of500
.
UOM:Jars
Formula:count * 5 / 500
Breakdown:
count
 the number of GPOs;
* 5
 to allow for 5 clips per count;
/ 500
 to get the proportion of the jar the clips are purchased in. 
Labour  to allow
30 minutes of Labour
per double GPO counted.
UOM:Hours
Formula:count * 0.5
Breakdown:
count
 the number of GPOs;
* 0.5
 to allow for half an hour per count.
The final measurement:
Mains Cable run
When measuring a mains cable run on a plan, there are also other parts and labour you may want to quantify:
 50mm HD Conduit  Calculate the number of
4m
lengths of conduit required
UOM: Lengths required
Formula: len/4
Breakdown:
len
 the number of meters measured;
/4
 to quantify one 4m
length for every 4
metres measured.
 50mm HD Conduit per 4m Lengths  Calculate the number of
4m
lengths of conduit required as a whole number
UOM: Lengths required
Formula: ceil(len/4)
Breakdown:
len
 the number of meters measured;
/4
 to quantify one 4m
length for every 4
metres measured;
ceil()
 to show the number of lengths required by rounding up a decimal value to the next whole number.

16mm XLPE  To calculate the length of cable and allow a
4m
drop per length measured to the switchboard.
Formula:len+count*4
Breakdown:
len
 the number of meters measured;
+count
 is the number of length runs measured;
* 4
 is to calculate4
meters of cable per length measured. 
16mm SDI Red To calculate
3
lengths of cable per meter measured and allow an extra2m
at each end of the cable lengths.
Formula:len*3+count*12
Breakdown:
len
 the number of meters measured;
* 3
 to allow for the3
lengths of cable required;
count
 the number of runs in the length measured (Please refer to the supported references for length measument.);
*12
to calculate2
meters each end of each of run for each of the3
lengths of cable required.
Enclosing your simple operations in a parenthesis will allow you to see your formulas better. As always, the formula bar follows the MDAS Rule, but the calculation will prioritise operations within a set of parentheses.

16mm SDI Black  To calculate the length of cable and allow an extra
2m at each end
per cable length.
Formula:len + count*4
Breakdown
len
 is the number of meters measured;
+count
 is the number of length runs measured;
* 4
 is to calculate2
meters of cable each end per length measured.
 Warning Tape 100m  to calculate the number of rolls of
100m
tape required per the length measured.
UOM:Rolls required
Formula:len/100
Breakdown:
len
 the number of meters measured;
/100
 to quantify one roll of tape for every 100 metres
measured.

50mm Sweeping Bend  count
2 sweeping bends
for each length measured.
UOM:EA
Formula:count*2
Breakdown:
count
 the number of lengths measured;
* 2
 to calculate2 bends
per length measured. 
Labour  to calculate
10 minutes
per meter of mains run.
UOM:Hours
Formula:count * 0.17
Breakdown:
count
 the number of GPOs;
* 17
 to allow for10 minutes
per meter measured.
The Final Measurement:
Airconditioning
When measuring a room area on a plan, you can use the room area to work out the KW rating required for an Airconditioner and the m3
volume for the room.

KW rating  Work out the kilowatt rating of a room or multiple rooms to ascertain the correct values for the unit size.
UOM:KW's
.
Formula:area*150/1000
Breakdown:
area
 is the square meters measured;
* 150
 is to calculate the wattage per meter squared;
/1000
 to convert this figure into a KW rating. 
m3 Volume  to work out the volume of air in a room or rooms with 2.7 meter high ceilings
UOM:m3
Formula:area * 2.7
Breakdown:
area
 the square meters measured;
* 2.7
 Multiplying the square meters by the ceiling height to get the air volume.
The Final measurement:
For additional formula assistance, please see our Measurement Parts & labour FAQs or click on help and click send us a message to contact one of our team.