Professional Lighting Calculator
Designed for Irish homes. Get accurate lumens, downlight counts and LED savings — calibrated for 2.4 m ceilings and Irish electricity rates.
Choose your room
Room dimensions
Lighting mood user adjustment
Mirror lighting
Standard 2.4 m Irish ceiling assumed. Results are practical estimates — perfect for planning your lighting layout before calling an electrician.
Your Results
Select your room and enter dimensions to see your tailored Irish lighting plan.
Use warm 2700K dimmable LEDs for that classic Irish cosy glow.
Switching 10 halogen GU10s to LEDs saves the average Irish home around €250 per year at current ESB rates. Payback in under 6 months.
Quick Lumens Estimator
A fast alternative calculator that factors in wall colour, ceiling height, and natural daylight. Perfect for a quick check before using the detailed lumen method above.
Methodology & Sources
Calculation method
This tool uses the lumen method — the standard photometric design approach used by lighting engineers across Ireland, the UK and Europe.
Work plane & Room Index k
This tool uses a work plane height of 0.75 m (CIBSE residential standard).
Mood multipliers — user adjustment (non-normative)
| Mood | Multiplier | Effect | Normative? |
|---|---|---|---|
| Cosy Warm | ×0.8 | Below CIBSE minimum — decorative/relaxation only | No |
| Standard | ×1.0 | CIBSE base lux — code-compliant result | Yes ✓ |
| Bright | ×1.3 | Above CIBSE minimum — well-lit, high-clarity | No |
| Task | ×1.6 | High-demand task areas, supplementary lighting | No |
Utilisation Factor (UF) table
| Room Index k | UF (used) | CIBSE typical range |
|---|---|---|
| < 0.75 | 0.42 | 0.38–0.46 |
| 0.75 – 1.0 | 0.50 | 0.46–0.54 |
| 1.0 – 1.5 | 0.57 | 0.53–0.61 |
| 1.5 – 2.0 | 0.62 | 0.58–0.66 |
| 2.0 – 3.0 | 0.68 | 0.64–0.72 |
| > 3.0 | 0.72 | 0.69–0.75 |
⚠️ For precise calculations, use the UF table from your specific luminaire's photometric datasheet.
Target illuminance values
| Room | Lux (this tool) | Source / basis |
|---|---|---|
| Living Room | 150 | CIBSE residential best practice |
| Kitchen (ambient) | 300 | CIBSE / SLL residential guide |
| Bedroom | 100 | CIBSE residential best practice |
| Bathroom (ambient) | 200 | CIBSE / SLL residential guide |
| Bathroom (mirror task) | +600 lm | CIBSE: 500 lux at face height |
| Home Office | 500 | EN 12464-1 §5.2 office tasks |
| Hallway | 100 | CIBSE residential best practice |
Referenced standards & sources
Recommended Lux Levels for Irish Homes
Different rooms require different lighting levels. The values below are based on EN 12464-1:2021 and CIBSE residential guidance, adapted for standard Irish ceiling heights of 2.4m.
| Room | Lux (ambient) | Typical use | Colour temp |
|---|---|---|---|
| Living Room | 150–300 | General relaxation and entertainment | 2700K |
| Kitchen | 300–500 | Food preparation and cooking | 3000–4000K |
| Bedroom | 100–200 | Rest and ambient lighting | 2700K |
| Bathroom | 200–400 | Grooming and hygiene tasks | 3000K |
| Home Office | 300–500 | Reading and computer work | 4000K |
| Hallway | 100–150 | Navigation and circulation | 2700–3000K |
Sources: I.S. EN 12464-1:2021 · CIBSE Code for Lighting 2022 · CIBSE LG09 Residential guidance.
How Many Lumens Do You Need Per Room?
Lumens measure the total light output of a fitting. Here are practical estimates for typical Irish room sizes, based on standard ceiling heights of 2.4m.
Living Room ~20 m²
A typical Irish sitting room needs at least 3,000 lumens for ambient lighting. Add floor lamps and table lamps to create layered light.
Kitchen ~12 m²
Plan for 300 lux ambient overhead, plus 500 lux over worktops via under-cabinet LED strips or targeted downlights.
Bedroom ~15 m²
Bedrooms benefit from lower ambient light (100 lux) with separate task lighting at bedside level.
Bathroom ~6 m²
Use IP65-rated fittings above the shower. Mirror lighting should provide 500 lux at face height.
Home Office ~10 m²
EN 12464-1 recommends 500 lux for sustained desk work. Invest in quality 4000K lighting to reduce eye strain.
Hallway ~8 m²
Space downlights every 1.2–1.5m along the run. Two fittings are more effective than one central point for halls over 4m.
LED Efficiency Comparison
Lumens per watt (lm/W) measures how efficiently a light source converts electricity into visible light. Modern LED technology is 6–10× more efficient than traditional incandescent bulbs.
For an Irish home running lights 5–6 hours per day, switching from halogen to LED typically saves €150–300 per year at current CRU rates (€0.43/kWh, April 2026).
Browse LED Bulbs →| Technology | Lumens per Watt | Lifespan | Efficiency |
|---|---|---|---|
| LED | 80–120 lm/W | 15,000–25,000h | |
| CFL | 45–75 lm/W | 6,000–15,000h | |
| Halogen | 15–25 lm/W | 1,000–4,000h | |
| Incandescent | 10–15 lm/W | 750–1,500h |
Source: SEAI — Sustainable Energy Authority of Ireland · EU Ecodesign Regulation 2019/2020
Lighting Calculator — Frequently Asked Questions
General lighting
What is a lumen?
A lumen (lm) measures the total amount of visible light emitted by a light source. A standard 60W incandescent bulb produces around 800 lumens. A modern 8W LED produces the same 800 lumens while using 87% less electricity.
What is lux?
Lux (lx) measures illuminance — the amount of light falling on a surface per square metre. One lux equals one lumen per square metre (1 lx = 1 lm/m²).
What is the difference between lux and lumens?
Lumens measure total light output from a source. Lux measures how much of that light reaches a surface. For room lighting calculations, lux is the useful measurement.
How do I calculate lighting requirements for a room?
The standard method is the lumen method: Total lumens = (Lux × Area) ÷ (UF × MF). This calculator does that automatically using EN 12464-1 values.
Room-specific
How many lumens do I need for a living room?
A typical Irish living room of 20 m² needs 3,000–4,500 lumens for standard ambient lighting at 150–225 lux. Use the calculator above with your exact dimensions for a precise figure.
How many lumens do I need for a kitchen?
A kitchen of 12 m² needs 3,600–6,000 lumens. Plan for 300 lux ambient plus 500 lux task lighting over worktops via under-cabinet LED strips.
How many lumens do I need for a bedroom?
A bedroom of 15 m² needs 1,500–3,000 lumens for ambient lighting at 100–200 lux. Dimmable fittings give the most flexibility.
How many downlights do I need?
Divide the total lumens required by the output of each downlight. A standard 550 lm GU10 LED means a 20 m² living room needing 4,000 lumens requires approximately 7–8 downlights.
Technical
What is Maintenance Factor (MF)?
Maintenance Factor (MF) accounts for the gradual reduction in light output over time. This calculator uses MF = 0.80, appropriate for modern LED sources in a clean residential environment.
What is Utilisation Factor (UF)?
Utilisation Factor (UF) describes what proportion of the light produced by a fitting actually reaches the work plane. This calculator uses generic UF values for standard GU10 downlights with typical Irish reflectances: ceiling 70%, walls 50%, floor 20%.
What lighting standard does this calculator use?
This calculator uses the lumen method as defined in EN 12464-1:2021 (I.S. EN 12464-1, published by NSAI) and the CIBSE Code for Lighting 2022. Work plane height is 0.75 m (CIBSE residential standard).
Can I use this calculator for commercial projects?
This tool is designed for residential use and provides indicative values only. For commercial projects, use luminaire-specific photometric data and consult a qualified lighting designer.
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Calculations follow EN 12464-1 lighting standards · Free tool by Lighting Dublin