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


 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)
  • Required No of Fixtures =21 No’s

 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.



  •  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



About Jignesh.Parmar
Jignesh Parmar has completed M.Tech (Power System Control), B.E(Electrical). He is member of Institution of Engineers (MIE) and CEng,India. Membership No:M-1473586.He has more than 16 years experience in Transmission -Distribution-Electrical Energy theft detection-Electrical Maintenance-Electrical Projects (Planning-Designing-Technical Review-coordination -Execution). He is Presently associate with one of the leading business group as a Deputy Manager at Ahmedabad,India. He has published numbers of Technical Articles in “Electrical Mirror”, “Electrical India”, “Lighting India”,”Smart Energy”, “Industrial Electrix”(Australian Power Publications) Magazines. He is Freelancer Programmer of Advance Excel and design useful Excel base Electrical Programs as per IS, NEC, IEC,IEEE codes. 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.

62 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


    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.

  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

  10. jagadeesh says:

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

  11. Madhan says:

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

    For your Reference:

    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

      • SUBRAMANI says:


        How will differ the lux level and No. of fixture based on height? Please explain in details

      • Rahat says:

        Thank You very much for your very important post. Could you tell me why 2 m height is not considered in evaluating the number of lights? So far I know, lumen and lux relationship calculation is based on 1m distant. So if it is 2 m, then why number of lights were not 2*21=42?

        Thanks and regards//Rahat Rubaiyat Islam

  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.

    • R K Veerabhadra Rao says:

      Assuming Metal Halide Lumens/watt = 80 Lumens/watt.

      Calculate Lumen per Fixtures:
      Lumen per Fixtures = Lumen Efficiency(Lumen per Watt) x each Fixture’s Watt
      Lumens for 1*400 W MH fitting = 400 * 80 = 32000 Lumens.

      Calculate No’s of Fixtures:
      Required No of Fixtures = Required Lux x Room Area / MFxUFx Lumen per Fixture
      Required No of Fixtures =(35x110x300) / (32000)
      Required No of Fixtures =36 No’s

  16. Alexander says:

    thank you sir for your knowledge sharing

  17. Alexander says:

    Let me know how to calculate lamp maintenance factor and utilization factor

  18. Shiv says:

    can i use room area for Sq. feet

  19. bennie says:

    is the SHR always given to be 1.25 if not how do i find it?

  20. can 110 W CFL provide proper illumination in 10 mtrs street lighting pole

  21. Shiv Shankar Kumar says:

    Plz . tell us how to calculate Space height Ratio , or 1.25 is fix .

  22. T says:

    need to consider the LOR? the actual lumens is lower then. please advise. thanks

  23. so how coms required no. of fixtures is 21 an i only c 20 fixtures there..

  24. Milind says:

    kindly elaborate how to calculate required nos. of tube light fixtures for industry based on required Lux level.

    • azeez says:

      dear friend…

      i am a electrical engineer now i am working as a electrical site engineer in steel plant industry ..please teach me the hole calculation of electrical in industrial and commercial lighting and power and transformer rating…….because hear nobody teach me…

  25. Joseliti Bulos says:

    What’s the MF and CU consideration for other types of lightings?

  26. Murali says:

    Dear Mr Jignesh, thanks for a splendid calculation chart which is very helpful for people like me. Since i do not find the input for mounting height of the luminaire, can you please explain me how the your calculation works so that it will give a better understanding of lighting design to me. Also may i request you to throw some light what happens if the fixture has some optics / particular beam angle for high ceiling factory applications and with COB LEDs as light source.

    Your suggestion and guidance will be highly appreciated. – Thanks Murali

  27. silas says:

    Dear Mr. Jignesh thank you very much for such a good illustration. Its give us clear concept.

    Silas Kahmei

  28. vismagneto says:

    Respected JigneshParmar sir i have a doubt we hav to design lighting systems for a commercial building in aroom such that each room have (625 SQ FT). so sir could u explain the calculation sir

  29. sir i have a doubt regarding the uf and mf calculations for led lights regarding the commercial buildings regarding the mall

  30. myat lion says:

    Thanks your advice. I can learn by using your idea.

  31. Abubakar Idris Ringim says:

    very interesting

  32. frank says:

    very good info

  33. b.k. meena says:

    how many led’s required for ceiling a hall of 6000squre feet in area

  34. venkataramana pila says:

    Thanks for creating blog

  35. Muhsin khan says:

    what is UF and MF

  36. Alan Bascon says:

    Mr. Jignesh, what if the height of the room varies?

  37. Amit Saxena says:

    An factory has a shed of 180 meter length 22 meter width and 13 meter height . They want 80w high bay LED light . How many light are installed and how much distance of installation one to another ?

  38. AUNG KHAING PHYO says:

    Hi Sir,
    which condition do we need to account for LOR ( lighting output ratio).
    And how can i find SHR value?

  39. AUNG KHAING PHYO says:

    Hi Sir,
    which condition do we need to account for LOR(LIghting Output Ratio) in?
    And how can i find SHR value? is it constant number?
    i am hoping answering back.

  40. hewan says:

    Dear Sir,

    Thank you for you tutorial on number of fixture and space required between them calculation,but i am facing some difficulties on understanding of SHR=1.25, MF, UF and lumen values so is this values are fixed or from where are we going to find these values.thank you

  41. Japhet Mutegi says:

    I have been looking for a detailed catalogue on UTILIZATION factors of various lighting fixtures. You may be having an answer to this. Kindly help. Thank you very much.

  42. Anubhavi Nagar says:

    If we are calculating light fittings for showroom…then hw to calculate maximum spacing required between each light fixture..


    jignesh ,great job,pl let me how to work out SHR,SPACE HEIGT RATIO.

  44. engr. John says:

    hi you have done a great work here best regards Engr. John

  45. Rajendra sahoo says:

    how calculate lux,if given data lumens-2400,beam angle-120,hight-1 m

  46. chandru v says:

    hi sir
    Can u explain how to select lighting fixture for residential building and commercial building

  47. atul says:

    room specification:-
    required lux=400
    total bulb=?

  48. atul says:

    how to calculate lux. please send lux calculation formule.

  49. A.G.Subramanian says:

    What is the COU to be considered for 45watts COB LED Flame proof well glass fiting

  50. Hoshang says:

    Gr8 work and your contribution to electrical sector.

  51. amir mahmood says:

    could you guide me about generally use utilization factor for LED lights

  52. mathias amankwah says:

    please, how do I determine the space to height ratio? is it a constant or some standard values?

  53. Dilushika gunawardana says:

    how we know the space to height ratio, MF & UF?

  54. pankaj datreliya says:

    For Service Road:-Pole Height 7mtr, Service road width 7.5mtr, pole to pole distance 23mtr, required 30lux and 4000k. how many wattage for led light fixture?

  55. pankaj datreliya says:

    For Bridge:-pole height 8 mtr, bridge width 16mtr pole installed in center berg area,pole to pole distance 23mtr, 30lux and 4000k,how many wattages required for led light fixture?

  56. ghulam hassan says:

    I need a lux calculation of our warehouse. total length is 30 meters width is 25 meter and the height is 15 meter at the center and at the end, height is 13.5 meter. I want to know how many high bay light can we used here and also a total load of these calculated light will consider in our mother panel.

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