Electrical Formulas

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.

Double GPO

When counting double GPO's on a plan there are also other parts and labour you may want to quantify.

1. Double GPO - to allow one double GPO per count

   Formula: count
   Breakdown:
   To quantify one part per count, the formula remains simply “count” as count x 1 = count.

2. Wall bracket - to allow one wall bracket per double GPO counted.
   Formula: count

3. 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.

4. 2.5mm twin and earth from a 100m cable drum - to allow 12m of cable per double GPO counted when you purchase cable in 100m 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.

5. 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 of 500.
   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.

6. 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:

1. 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.

2. 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.

3. 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 calculate 4 meters of cable per length measured.

4. 16mm SDI Red -To calculate 3 lengths of cable per meter measured and allow an extra 2m at each end of the cable lengths.
   Formula: len*3+count*12

   Breakdown:
   len - the number of meters measured;
   * 3 - to allow for the 3 lengths of cable required;
   count - the number of runs in the length measured (Please refer to the supported references for length measument.);
   *12 to calculate 2 meters each end of each of run for each of the 3 lengths of cable required.

5. 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 calculate 2 meters of cable each end per length measured.

6. 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.

7. 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 calculate 2 bends per length measured.

8. 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 for 10 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.

1. 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.

2. 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.