LED Strip Calculator (Free Tool, 2026)

How much LED strip do you need behind your TV, around a room or under your kitchen cabinets? This free LED strip calculator works out the exact length to buy, how many kits you need, the right power supply size and what the strip will cost to run each month. It works in metres or feet and covers RGBIC, RGBWW and COB strips.

How the LED Strip Calculator Works

The calculator measures the run you choose, then adds 10% for corners, connectors and routing the strip to the power outlet. For TV backlighting it uses your screen size and the standard 16:9 shape to estimate the perimeter of the back of the TV, keeping the strip slightly inside the edges so it stays hidden. For rooms it uses the ceiling perimeter, and for cabinets and shelves it uses the total length you enter.

Power is estimated per metre for each strip type: around 5 watts per metre for typical RGB and RGBIC strips, about 6 watts for RGBWW strips with dedicated white LEDs, and about 10 watts for dense COB strips. The recommended power supply includes about 20% headroom so the adapter does not run at its limit. Running cost uses your average brightness, hours per day and electricity rate.

How to Measure for LED Strip Lights

• Behind a TV: measure the back of the screen about 5 cm in from each edge. Choose three sides if the TV sits on a stand and the bottom edge is hidden.
• Ceiling or cove: measure every wall where the strip will run, including alcoves, and add the distance back to the outlet.
• Under cabinets: measure the underside of each cabinet run and the gaps between them if the strip will jump across.
• Shelves: measure the front lip or back edge of each shelf you want to light.

Always measure the path the strip will actually follow, not just the width of the wall. Corners and cable routing add more length than most people expect.

Choosing the Right LED Strip Type

RGB and RGBIC

Best for colour effects, gaming setups and TV backlights. RGBIC strips can show several colours at once along the strip. The white light is less natural than strips with dedicated white LEDs.

RGBWW

Adds dedicated warm and cool white LEDs, so everyday white light looks much more natural. A good choice for living rooms, bedrooms and ceiling coves.

COB

Chip-on-board strips pack LEDs so densely that the light looks like a continuous line with no visible dots. Ideal under kitchen cabinets, on shelves and anywhere the strip is visible.

For brand-specific picks, see our Govee lights guide. To work out how bright a whole room should be, try our lumens calculator, and to see how much switching to LED saves, use the LED vs incandescent savings calculator.

LED Strip Power Supply Tips

• Match the voltage of the power supply to the strip (5V, 12V or 24V).
• Choose a supply rated at least 20% above the strip’s maximum wattage.
• Long 5V runs dim towards the end; 12V and 24V strips handle longer distances better.
• For very long runs, feed power from both ends or use a second power supply as the manufacturer recommends.
• Keep power supplies ventilated and never cover them with insulation or fabric.

LEDs are very efficient. The U.S. Department of Energy notes that quality LED lighting uses far less energy and lasts much longer than incandescent lighting, which is why even long strips cost only a few dollars a year to run.

Frequently Asked Questions

How many metres of LED strip do I need for a 65-inch TV?

For all four sides of a 65-inch TV, you need about 4 to 4.5 metres including a little extra for corners, so a 5-metre kit is usually the right choice.

How much LED strip do I need for a room?

Add up the length of every wall the strip will follow, then add about 10%. A 4 by 3.5 metre room needs about 15 metres plus extra, so roughly 16 to 17 metres.

How much does it cost to run LED strip lights?

Very little. A 5-metre strip drawing about 25 watts at full brightness, running four hours a day at 70% brightness, costs around $4 a year at $0.17 per kWh.

Can I connect two LED strips together?

Often yes, using the manufacturer’s connectors or extension kits, but check the maximum run length per power supply. Mixing different brands or types is not recommended.

What size power supply do I need for my LED strip?

Multiply the strip length by its watts per metre, then add about 20%. A 5-metre strip at 5 watts per metre needs at least a 30-watt supply, so a 36-watt adapter is a safe choice.

More guides: best smart lighting for your living room, best smart light bulbs and smart home energy saving tips.