# Calculate No of Lighting Fixtures / Lumen for Indoor Lighting

• An office area is 20meter (Length) x 10meter (width) x 3 Meter (height). The ceiling to desk height is 2 meters. The area is to be illuminated to a general level of 250 lux using twin lamp 32 watt CFL luminaires with a SHR of 1.25. Each lamp has an initial output (Efficiency) of 85 lumen per watt. The lamps Maintenance Factor (MF) is 0.63 ,Utilization Factor is 0.69 and space height ratio (SHR) is 1.25

## Calculation:

### Calculate Total Wattage of Fixtures:

• Total Wattage of Fixtures= No of Lamps X each Lamp’s Watt.
• Total Wattage of Fixtures=2×32=64Watt.

### Calculate Lumen per Fixtures:

•  Lumen per Fixtures = Lumen Efficiency(Lumen per Watt) x each Fixture’s Watt
• Lumen per Fixtures= 85 x 64 = 5440Lumen

### Calculate No’s of Fixtures:

•  Required No of Fixtures = Required Lux x Room Area / MFxUFx Lumen per Fixture
• Required No of Fixtures =(250x20x10) / (0.63×0.69×5440)

### Calculate Minimum Spacing Between each Fixture:

•  The ceiling to desk height is 2 meters and Space height Ratio is 1.25 so
• Maximum spacing between Fixtures =2×1.25=2.25meter.

### Calculate No of Row Fixture’s Row Required along with width of Room:

•  Number of Row required = width of Room / Max. Spacing= 10/2.25
• Number of Row required=4.

### Calculate No of Fixture’s required in each Row:

•  Number of Fixture Required in each Row = Total Fixtures / No of Row = 21/4
• Number of Fixture Required in each Row = 5 No’s:

### Calculate Axial Spacing between each Fixture:

•  Axial Spacing between Fixtures = Length of Room / Number of Fixture in each Row
• Axial Spacing between Fixtures =20 / 5 = 4 Meter

### Calculate Transverse Spacing between each Fixture:

•  Transverse Spacing between Fixtures = width of Room / Number of Fixture’s row
• Transverse Spacing between Fixtures = 10 / 4 = 2.5 Meter.

## Conclusion:

•  No of Row for Lighting Fixture’s= 4 No
• No of Lighting Fixtures in each Row= 5 No
• Axial Spacing between Fixtures= 4.0 Meter
• Transverse Spacing between Fixtures= 2.5 Meter
• Required No of Fixtures =21 No’s

Jignesh Parmar has completed his B.E(Electrical) from Gujarat University. He has more than 11 years experience in Power Transmission-Power Distribution-Electrical energy theft detection-Electrical Maintenance-Electrical Projects(Planning-Designing-coordination-Execution). He is Presently associate with one of the leading business group as a Assistant Manager at Ahmedabad,India. He is Freelancer Programmer of Advance Excel and design useful Excel Sheets of Electrical Engineering as per IS,NEC,IEC,IEEE codes. He is technical Author for "Electrical Mirror" and "Electrical India" Magazines. He is Technical Blogger and Familiar with English, Hindi, Gujarati, French languages. He wants to Share his experience & knowledge and help technical enthusiasts to find suitable solutions and updating themselves on various Engineering Topics.

### 17 Responses to Calculate No of Lighting Fixtures / Lumen for Indoor Lighting

1. Basavaraj says:

Jignesh Parmar your doing awesome work and great help to us thank you sir

2. KARZAN N. ESMAIL says:

Thanks for your great work ,,,,,,, best regards

3. MD SHAHWAZ RIZVI says:

Thanks for the blog.
These blog are very helpful for us.
I Rizvi as an Electrical Engineer say that You are doing a great work for a manking.Sharing Knowledge is the world happiest thing to do.

4. gustavo rafael faquira soto says:

gracias colega…exitos…

5. Subrata Roy says:

Found very correct . This is a thumb rule type of design – and it is the best approach for the electrical engineers like us . A really thankful Job . Here I want to request you to discuss the importance of Polar Curves of verious lamps for illumination design if possible . Thanks .

6. showman says:

I want to buy salary software but I am bangladeshi so no way to send money. Please give me a right way to send maney.
ASAP.

7. sanjeev Pareek says:

great work. concise and useful.

8. muqtar says:

thanks for useful article, and sir please load standard lux level chart and please explain lumen per watt, U.F, M.F AND SHR

Thanking you,

9. vijaykumar says:

Helping a lot with ur kno wledge

jignesh paramer ,your material is very useful to me ,plz suggest me design courses for electrical.I want to built-up career in design.

Could you explain how did you take “total fixtures=21″

Calculate No of Fixture’s required in each Row:
Number of Fixture Required in each Row = Total Fixtures / No of Row = 21/4
Number of Fixture Required in each Row = 5 No’s:

• Calculate No’s of Fixtures:
Required No of Fixtures = Required Lux x Room Area / MFxUFx Lumen per Fixture
Required No of Fixtures =(250x20x10) / (0.63×0.69×5440)
Required No of Fixtures =21 No’s

12. Nagaraj says:

Can u please refer me the book where i can completely know about lighting design both indoor and outdoor, kindly help me in this matter

13. vamsi says:

excelent work sir, could u plz explain how to chose lux value for a room.

14. Crestian says:

Great and useful work

15. P.Siva says:

Dear Sir
I need one clarification from you …..Here i am giving Factory size in mt(35M width *110Mtr Length)and Our required lux level (300Lux).light requirements for 1*400W metal halide fitting.Our buliding ht is 14.0Mtr.Cealing type made by Sheet. How many fittings required.Then how to calculate detailed formula required sir.