Corners, returns and the bits that get forgotten
Corners are where estimates go wrong. A cove that turns three corners is four straight legs plus four transitions, and each transition either takes a small connector piece or forces the strip to break and restart. Measure the legs to the inside face of each corner and note the turn as a separate item.
Two more habitual omissions. The first is the return leg, the short stretch that comes back along the end of a peninsula or the side of a bulkhead. The second is the drop from the run to wherever the lead exits. Neither shows on a floor plan, and both need tape.
Add an allowance for cut intervals and joins
Strips do not shorten anywhere you like. Each product publishes a cut interval, and a length only reduces to the nearest one, so a leg measuring 46 inches on a product with a long interval may have to be installed at the next size up. Multiply that effect by every leg on the job.
Add an allowance for joins too. Every point where two lengths meet consumes a little tape during stripping or soldering, and any cut made badly is tape you cannot use. Whether a strip is rejoined with a matched connector or with solder after a cut at its marked point is set by the product, so check the method and the pin count against the connector and wire range before finalizing the figure.
A worked example: how much LED strip do I need for a kitchen?
Take a kitchen with three under cabinet legs of 42, 30 and 54 inches, plus a 16 inch return. That is 142 inches, or 11 feet 10 inches. Round up to 12 feet for the cut intervals, then add an allowance for joins and one spoiled cut, which takes you to 13 feet.
Now check that total against the product. A 13 foot continuous run may sit inside one product's published maximum run and outside another's, which changes whether you need one feed or two. Our guide to maximum run length explains what happens past that limit.
Turn the footage into watts before choosing a supply
The measured total does double duty. Take the watts per foot published for the strip you chose, multiply it by your final footage, and you have the load the supply must carry. Then pick a unit rated at least 20 percent beyond that load so it is not sitting at its limit (verify the current headroom guidance and the published rating before ordering).
To keep the arithmetic visible, take an illustrative figure of 3 watts per foot across 13 feet. That is 39 watts, and 20 percent headroom lifts the target to 46.8 watts. Substitute the actual published watts per foot for your product, because the figure varies considerably between output tiers in the LED strip range.
Keep voltage matched exactly, 24V tape to a 24V supply, and bring each leg back to the supply in parallel rather than chaining one behind another. Where a supply is hardwired, or a junction box or wall device is involved, that is electrician territory: local code, the NEC where it applies, and the instructions shipped with the unit govern it.
Order spare from the same purchase
Buy a little more than the calculation says, and buy it at the same time. LED output and color can vary between production batches, which is why a replacement piece bought a year later can read slightly different against the original even at the same nominal color temperature. Our note on batch variation and color consistency covers why.
Spare also covers the leg you mismeasured. On a high brightness product like the LEDClub 24V COB 500 Series, confirm the published watts per foot and cut interval before translating feet into an order (verify both before you rely on them).
