LED Strip Length & Power Calculator
An undersized power supply will overheat, flicker, or fail early, while an oversized one wastes money and space. Enter your total strip run length and density below to find the right power supply rating.
Work out your LED strip power needs
Enter your total strip run length and pick its density.
Total strip wattage: 24.0W
36W power supply recommended
This includes roughly 20% headroom above the strip's draw, which helps the power supply run cooler and last longer.
Recommended products
A few well-reviewed LED strip lighting kits to consider.
- Remote control
£25.99
Pros
- Ultra-thin 5mm strip fits tight under-cabinet and shelf gaps
- 600 LEDs across 5m give even colour coverage
- Remote control included for instant colour and brightness changes
Cons
- Remote has no scheduling or app integration
- Plug & dimmer switch (no app)
£14.43
Pros
- 1650 lumens of warm white light across 300 LEDs
- Physical dimmer switch included, no app needed
- Flexible tape cuts to size for kitchens, wardrobes and stairs
Cons
- No colour-changing or smart-home features
- Wi-Fi
£24.99
Pros
- Direct Wi-Fi connection, no separate hub required
- Works with Alexa and Google Assistant for voice control
- Music sync mode reacts to sound in real time
Cons
- Requires a stable 2.4GHz Wi-Fi network to stay connected
Frequently asked questions
Why does my LED strip need a power supply bigger than its rated wattage?
Running a power supply right at its maximum rating causes it to run hot and wear out faster, so sizing up by around 20% gives it headroom and helps it last longer, especially if you run the strip for long periods.
Can I connect multiple LED strip runs to one power supply?
Yes, as long as the combined wattage of all the runs stays within the power supply's rated output including headroom, though for longer total runs it's often better to use several smaller supplies spread along the run to avoid voltage drop.
What is voltage drop and does it affect my LED strip?
Voltage drop happens when a strip run gets long enough that the far end receives less voltage than the near end, causing it to look dimmer or shift colour, so very long single runs benefit from being powered from both ends.
Does a denser, brighter LED strip really use three times the power?
Yes — a dense or high-brightness strip typically has around three times as many LEDs per metre as a standard strip, so it draws roughly three times the wattage and needs a correspondingly larger power supply for the same length.
How this calculator works
The LED strip length calculator works by taking the total length of your LED strip run in metres (m) as input. The calculator then multiplies this length by the typical power consumption per metre of that specific type of LED strip, which we've based on commonly available UK products. We assume a standard operating voltage of 12V DC for most LED strips – this is the most common configuration found in the UK market. It’s crucial to check the manufacturer’s specifications for your chosen strip to ensure accurate power consumption figures.
Once the total wattage is calculated, the calculator determines the required amperage of your power supply. This is done by dividing the total wattage by the operating voltage (12V). The result is then used to select a power supply with sufficient current capacity – always choose a power supply with an amperage rating higher than the calculated value for safety and stability, ideally 20% higher.
LED Strip Power & Voltage Guide (UK)
| LED Strip Type | Typical Wattage per Metre (Watts/m) | Operating Voltage (V DC) | Typical Price (£) |
|---|---|---|---|
| IP65 Waterproof LED Strip | 1.4 | 12V | £25-£40 |
| Warm White LED Strip (3500K) | 2.8 | 12V | £18-£30 |
| Cool White LED Strip (6000K) | 3.2 | 12V | £22-£35 |
| RGB LED Strip | 2.5 | 12V | £30-£50 |
| Single Colour LED Strip (Red/Green/Blue) | 3.0 | 12V | £28-£45 |
Worked example: Lighting a UK Shed
Let’s say you want to illuminate a small shed (approximately 2m x 3m) with LED strip lighting. You decide to use 10 metres of warm white LED strips, costing approximately £28 per roll and having a wattage of 2.8 Watts/m. Plugging these figures into the calculator gives us a total power consumption of 10m * 2.8W/m = 28 Watts. To calculate the required amperage, we divide this by 12V: 28W / 12V = 2.33 Amps.
Therefore, you would need a 12V DC power supply with a minimum current rating of 2.5 Amps (to allow for headroom). A readily available power supply in the UK would be a 12V 3A power adapter – this would provide sufficient power and safeguard against potential overloading. The total cost for this setup, including the LED strip and power supply, would likely be around £70-£95 depending on where you source your components.
More questions answered
What if my LED strip has a different voltage than 12V?
The calculator is primarily designed for 12V DC LED strips, which are the most common in the UK. If your strip uses a different voltage (e.g., 24V or 5V), you’ll need to adjust the input length accordingly and ensure the power supply matches that specific voltage. Always check the manufacturer's specifications before using the calculator.
How accurate are the wattage figures for LED strips?
LED strip wattage figures provided by manufacturers can vary slightly due to tolerances in production. We’ve used typical values based on commonly available UK products, but it’s always best to double-check the product specifications before use. Small variations won't drastically affect the overall calculation.
What if I want to run multiple LED strips in parallel?
If you intend to connect multiple LED strips in parallel (i.e., they share the same power supply), simply add up the wattage of each strip before entering it into the calculator. Ensure that your chosen power supply has sufficient amperage capacity for the combined wattage.
What does ‘amperage’ mean and why is it important?
Amperage (measured in Amps or A) represents the amount of electrical current flowing through a circuit. A higher amperage requirement means your power supply needs to be capable of delivering more electricity. Overloading a power supply can cause flickering, dimming, or even damage.
What happens if I use a power supply with too low an amperage?
Using a power supply with insufficient amperage will likely result in the LED strip flickering intermittently or dimming significantly. This is because the power supply isn't able to provide enough current to consistently power the strip. It’s crucial to select a power supply that meets or exceeds the calculated requirements.
Can I use this calculator to calculate the wattage for RGB LED strips?
Yes, you can! RGB LED strips typically have higher wattage per metre than single-colour strips. Make sure to input the correct wattage value specified by the manufacturer for your chosen RGB strip.
What is the impact of UK electricity prices on my calculations?
The calculator doesn’t directly factor in electricity prices, but it helps you determine the *power* needed (measured in Watts). Your electricity bill will then be based on how much power you consume over a period of time – a higher wattage LED strip will naturally result in a higher energy cost.
I'm using this for an outdoor project - does weatherproofing matter?
Absolutely! Ensure that your chosen LED strips and power supply are appropriately rated for outdoor use. Look for IP (Ingress Protection) ratings – IP65 or higher is recommended for protection against rain and splashes, while IP44 offers basic protection. Always connect electrical components outdoors with weatherproof connectors.
What if I'm unsure about the wattage of my LED strip?
Consult the manufacturer’s specifications on the product packaging or website. If you can’t find this information, contact the retailer for assistance – many retailers offer technical support for their products.
Can I use this calculator to size a power supply for multiple lights?
Yes, but remember to add up the wattage of *all* the LED strips or lighting fixtures you intend to connect in parallel. It’s always better to slightly overestimate your power supply's capacity than to risk overloading it.