Free engineering tool
Street light pole height & spacing calculator
Enter the road width, pole height and luminaire output. The calculator recommends single-sided, staggered or opposite poles and the maximum spacing that still reaches the lighting class, using the lumen method with a uniformity limit.
Method
The lumen method balances the light leaving the luminaires against the light needed on the road: spacing = n × Φ × UF × MF ÷ (E × W), where n is the number of luminaires per spacing (1 for single-sided, 2 for staggered and opposite), Φ the luminaire lumens, UF the utilisation factor (the share of light that lands on the road), MF the maintenance factor, E the target average illuminance and W the road width.
Light output alone is not enough: if poles are too far apart, the road gets dark patches between them. The calculator therefore caps the spacing at 3.5 × the mounting height, a common limit for modern LED road optics, and tells you when a lower wattage would already reach the target at that spacing.
Worked example
A 7 m two-lane road, class M3 (about 15 lx average), 10 m poles, 100 W luminaires at 130 lm/W. Road width ÷ height is 0.7, so single-sided poles are recommended. Φ = 13,000 lm, UF ≈ 0.43, MF 0.8, so spacing from light output = 13,000 × 0.43 × 0.8 ÷ (15 × 7) ≈ 42.7 m. The uniformity limit is 35 m, so the recommended spacing is 35 m, and about 82 W (a 90 W luminaire) would already reach 15 lx at that spacing.
Lighting classes
EN 13201 classes: M classes for motorised traffic (specified in luminance, converted here at about 15 lx per cd/m² for dry asphalt), C classes for conflict areas such as junctions, and P classes for pedestrian and residential streets. US designers use IES RP-8 values, which are of similar magnitude.
Questions about this calculation
What is the typical spacing for street lights?
For LED road optics, spacing is usually 3 to 4 times the mounting height: about 25–35 m for 8–10 m poles and 35–45 m for 12 m poles. The exact value depends on road width, lighting class and the luminaire photometry. Closer than 2 × the mounting height usually means the luminaire is too weak for the pole.
When should poles be single-sided, staggered or opposite?
A common rule: single-sided when the road is no wider than the mounting height, staggered when it is up to about 1.5 times the mounting height, and opposite (twin) for wider roads. Dual carriageways often use central twin-arm poles in the median instead.
How high should street light poles be?
Residential streets and paths: 4–6 m. Collector and urban roads: 8–10 m. Main roads and highways: 10–14 m. Junctions, roundabouts and interchanges: high masts of 15–30 m. A higher pole allows wider spacing but needs more lumens per luminaire.
Is this a replacement for DIALux?
No. It is a quick lumen-method estimate for early planning and budgets. Final road designs must be checked with the luminaire photometric file for luminance or illuminance, uniformity and glare. We run those checks free for projects using our luminaires.
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Next step
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