Calculator
Select a mode, enter geometry, then add allowances for corners, leads, and slack.
Example data
A typical cove lighting perimeter example with practical allowances.
| Item | Example input | Example output |
|---|---|---|
| Mode | Room perimeter (rectangle) | Base length = 2 × (L + W) |
| Room size | L = 12 m, W = 7.5 m | Base length = 39.00 m |
| Openings | Deduct 1.2 m (door gap) | Adjusted base = 37.80 m |
| Allowances | 4 corners × 0.10 m, leads 2 × 0.20 m | Pre-slack = 38.60 m |
| Slack | 10% | Required = 42.46 m |
| Cut increment | 0.05 m | Rounded = 42.50 m |
| Reel length | 5 m | Reels needed = 9 (45.00 m purchased) |
| Power density | 14.4 W/m at 12 V | Total ≈ 612 W, current ≈ 51 A |
Electrical outputs are planning values; always confirm with manufacturer limits and cable sizing.
Formulas used
- Perimeter mode: Base = 2 × (L + W) − openings.
- Segments mode: Base = Σ (segment length × count).
- Grid mode: Runs = ceil(width ÷ spacing) + 1, Base = Runs × run length (direction dependent).
- Allowances: Pre-slack = Base + (corners × corner allowance) + (lead ends × lead length).
- Slack factor: Required = Pre-slack × (1 + slack% ÷ 100).
- Cut rounding: Rounded = ceil(Required ÷ cut increment) × cut increment.
- Reels: Reels = ceil(Rounded ÷ reel length), Purchased = Reels × reel length, Waste = Purchased − Rounded.
- Power: Total W = power density × Rounded, Recommended W = Total W × (1 + headroom% ÷ 100).
- Current: Amps = Watts ÷ Volts (total and per feed).
- Feeds: Feeds = ceil(Rounded ÷ max run per feed).
How to use this calculator
- Choose units and a calculation mode that matches your layout.
- Enter geometry: perimeter dimensions, segments, or grid spacing.
- Add allowances for corners, lead tails, and a realistic slack percentage.
- Set strip cut increment and reel length to reflect your product.
- Enter power density, voltage, max run, and headroom for sizing.
- Click Calculate to see length, reels, and electrical load.
- Use the download buttons to export the latest results.
Tip
For long installations, feed power from both ends or inject mid-run to reduce dimming.