Reflector Size Calculator

Calculator Inputs

Bed length (m)

Enter the planting bed or canopy length.

Bed width (m)

Enter the planting bed or canopy width.

Mounting height above canopy (m)

Distance from reflector to plant tops.

Beam spread angle (deg)

Typical reflectors range from 60–120 degrees.

Coverage shape

Choose the footprint model you prefer.

Overlap allowance (%)

Extra coverage helps reduce banding between lights.

Reflector efficiency (0–1)

Polished surfaces often score higher than dull.

Edge loss estimate (%)

Accounts for dark edges and spill losses.

Evaluate with light count (optional)

Enter an existing count to check coverage.

Reflective lining height (m)

Sidewall or barrier height around the bed.

Waste allowance (%)

Covers trimming, seams, and overlaps.

Include base lining area

Useful for reflective floors or benches.

Example Data Table

Scenario	Bed (m)	Height (m)	Spread (deg)	Shape	Efficiency	Edge loss	Recommended lights	Opening (m)
Compact herbs	1.2 × 1.2	0.6	90	Rect	0.85	5%	2	1.200
Leafy greens	2.0 × 1.0	0.7	100	Rect	0.88	6%	2	1.669
Seedling trays	1.5 × 0.9	0.5	80	Circle	0.82	5%	2	0.839

Values are illustrative. Your exact outputs depend on overlap and losses.

Formula Used

r = h × tan(θ/2)

Where h is mounting height and θ is beam spread.

Opening (D or S) = 2r

Use diameter for circular footprint, side for square footprint.

A_circle = π × (D/2)²

A_rect = S²

A_usable = A × efficiency × (1 − edge_loss)

A_design = A_target × (1 + overlap)

Lights = ceil(A_design ÷ A_usable)

How to Use This Calculator

Measure your bed length and width at the canopy.
Enter the mounting height from reflector to leaves.
Choose a spread angle based on your reflector type.
Set overlap and losses to match your real setup.
Press Calculate to see opening size and light count.
Use downloads for records, quotes, or installation notes.

Practical tip: keep reflective surfaces clean and wrinkle-free.

Uniformity and edge control

Reflector sizing is a practical way to manage light uniformity across beds and benches. The calculator converts mounting height and beam spread into an opening footprint at the canopy. When you add overlap allowance, the design area increases to reduce banding between fixtures. Edge loss accounts for spill and weaker perimeter intensity, improving realism for reflective hoods and simple baffles. This supports repeatable planning for indoor racks, trays, and small tunnel covers.

Opening footprint at canopy

The footprint is built from basic geometry: radius equals height times the tangent of half the spread angle. For a rectangular model, the opening side is twice that radius; for a circular model, the opening diameter is the same. These two options help match your equipment style and layout preferences when planning bed coverage. A wider spread increases footprint but can lower intensity, so balance coverage and plant requirements.

Usable coverage and reflector performance

Ideal footprint area is adjusted using reflector efficiency and an edge-loss factor. Clean, polished surfaces typically maintain higher efficiency, while dull, dusty, or wrinkled surfaces reduce it. The usable area per light is the key driver for the recommended fixture count, because it represents the portion of the footprint that reliably contributes to the design target. Document your cleaning schedule because performance drift is gradual and easy to overlook.

Fixture count and coverage check

The calculator recommends lights by dividing the design area by usable area per light and rounding up. You can also enter an existing light count to evaluate achievable coverage percentage. If coverage is below 100%, increase overlap, improve efficiency, add fixtures, or adjust height and spread to restore uniformity.

Reflective lining planning

Beyond the reflector opening, the tool estimates reflective lining area using bed perimeter and lining height, with an optional base area. A waste allowance supports seams and trimming. This helps you quantify film or panel needs for small enclosures, sidewalls, and bench surrounds while keeping procurement and installation decisions consistent.

FAQs

1) What spread angle should I enter?
Use the manufacturer’s listed beam spread if available. If unknown, start with 90 degrees for many general reflectors and tune the value until the footprint matches observed coverage.

2) Why does edge loss matter?
Light intensity often drops near the footprint boundary due to spill and reflector imperfections. Adding edge loss reduces optimistic coverage estimates and supports more even canopy results.

3) How do I choose overlap allowance?
Overlap improves uniformity where footprints meet. For tight spacing, 5–15% is common. Increase overlap if you see striping, hotspots, or uneven growth patterns.

4) What does reflector efficiency represent?
Efficiency is a simplified factor for how much useful light is directed toward the canopy. Dirt, dents, wrinkles, and aging materials can reduce effective performance.

5) Can I use this for sunlight reflectors outdoors?
Yes, as an approximation for reflective panels and baffles. Outdoor wind, sun angle, and seasonal changes add variability, so treat results as planning guidance.

6) How should I use the lining area output?
Use it to estimate reflective film or panel quantity. Add waste for seams and trimming, and verify the final layout on site before purchasing large rolls.