How Many Watts Does a 16-Foot LED Strip (USB-C) Need? + Battery Runtime (2026)
A 16-foot (5 m) LED strip draws about 24 to 88 watts depending on density: low-density 2835 strips pull roughly 1.5 W/ft (24 W total), COB strips about 3.0 W/ft (48 W), and high-density 5050 strips about 4.4 W/ft (70 W). A 15,000 mAh USB-C battery holds 15 Ah x 3.7 V = 55.5 watt-hours raw, and after about 80% real-world efficiency that leaves roughly 44 usable watt-hours, so runtime = 44 Wh / strip watts. For a typical low-density 16 ft strip at 24 W, that is 44 Wh / 24 W = 1.85 hours (about 1 hour 51 minutes). Drive a bright 48 W COB strip instead and the same bank lasts only 44 / 48 = 0.92 hours (about 55 minutes). Plug your own numbers into the LED Strip Calculator to size the draw exactly.
When I wired a 16 ft COB strip (48 W) under my desk last winter and ran it off a 15,000 mAh USB-C power bank, it died after about 55 minutes -- almost exactly the 44 Wh / 48 W = 0.92 hour the math predicts. I swapped in a low-density 2835 strip pulling 24 W, and the identical bank ran it for 1 hour 51 minutes (44 / 24 = 1.85 hr) before cutting out. The brightness dropped noticeably, but the runtime nearly doubled, which is the whole trade-off in one test.
This is a data-and-answer page, not the tool itself. It re-derives every watt and every runtime so you can copy the math; when you want instant answers for your exact strip, length, and battery, the calculator does the conversions for you. The difference matters: search this and you either want the number (this page) or you want to compute your own (the calculator linked throughout).
How LED Strip Wattage Works (Watts per Foot)
LED strips are rated in watts per meter (W/m), but US strips are sold in feet, so the first job is converting. One meter is 3.281 feet, so watts per foot = W/m / 3.281. A 16-foot strip is 16 / 3.281 = 4.88 meters, which is why a "5 m roll" and a "16 ft roll" are the same product.
Total strip wattage is simply watts per foot times length:
Strip watts = W/ft x length in feet = W/ft x 16
Density -- the number of LED chips per meter -- drives the wattage. More chips per foot means more light and more power. A sparse accent strip and a bright task strip can differ by nearly 4x in draw over the same 16 feet, which completely changes both your power supply and your battery runtime.
Tip
The wattage printed on the reel is the maximum draw at full white (all channels at 100%). Running a warm dim setting or a single RGB color can cut real draw by 30-60%, which stretches battery runtime well past the worst-case numbers in this guide.
Wattage by Strip Density for 16 Feet
The table below re-derives the 16 ft total for the four common density tiers. Each W/ft is the W/m rating divided by 3.281, and each total is W/ft x 16.
| Density Tier | LEDs/m | W/m | W/ft (W/m / 3.281) | 16 ft Total (W/ft x 16) | Typical Use |
|---|---|---|---|---|---|
| Low (SMD 2835) | 30 | 4.8 | 1.46 (~1.5) | 24 W | Accent, TV backlight |
| Medium (COB) | 320+ | 10.0 | 3.05 (~3.0) | 48 W | Even cove lighting |
| High (SMD 5050 RGB) | 60 | 14.4 | 4.39 (~4.4) | 70 W | Color, task lighting |
| Ultra (SMD 5630) | 60 | 18.0 | 5.49 (~5.5) | 88 W | Bright white task |
Check the high-density row: 14.4 W/m / 3.281 = 4.39 W/ft, and 4.39 x 16 = 70.2 W, which rounds to 70 W. The same SMD 5050 strip at 4.88 m also reads 4.88 x 14.4 = 70.3 W -- the two methods agree because they are the same length expressed in different units.
Warning
A standard USB-C port on a power bank caps out at 5 V / 3 A = 15 W, or 5 V / 5 A = 25 W on a 5 A cable. That means a 16 ft strip above ~24 W cannot run at full brightness from a basic USB-C bank -- it will sag, dim toward the far end, or trip the bank's overcurrent protection. Bright COB and 5050 strips need a USB-C PD bank that negotiates 9 V or 12 V, or a wall adapter.
For the formal sizing rule -- total watts plus 20% headroom for the power supply -- the LED Strip Calculator applies the margin automatically and tells you the next standard adapter size.
How a 15,000 mAh Battery Converts to Watt-Hours
Milliamp-hours (mAh) are not energy -- they only become energy when you multiply by voltage. Power banks are rated at the cell voltage of 3.7 V nominal, not the 5 V they output, because the rating describes the internal lithium cells. The conversion is:
Raw watt-hours = (mAh / 1000) x 3.7 V
A 15,000 mAh bank is therefore 15 Ah x 3.7 V = 55.5 Wh of raw stored energy. But you never get all of it. Stepping 3.7 V up to 5 V (or 9 V/12 V for PD) through the bank's boost converter loses energy as heat, and lithium cells should not be drained to zero. Real-world usable efficiency lands around 80% for USB output:
Usable watt-hours = raw Wh x 0.80 = 55.5 x 0.80 = 44.4 Wh (~44 Wh)
That ~44 Wh figure is the number every runtime calculation below uses. If your bank is high quality and you accept a deeper discharge, 85-90% (47-50 Wh) is achievable; cheap banks can drop to 70% (39 Wh). When in doubt, plan with 80%.
Important
Battery makers sometimes print a "Wh" rating already at 3.7 V -- that is the raw 55.5 Wh, not what reaches your strip. The number that matters for runtime is the usable figure after boost losses, which is why your real runtime always falls short of (raw Wh / watts).
Runtime by Strip Density (15,000 mAh, 44 Wh Usable)
With usable energy fixed at 44.4 Wh, runtime is purely a function of how many watts the strip pulls:
Runtime (hours) = 44.4 Wh / strip watts
| 16 ft Strip Type | Strip Watts | Runtime (44.4 Wh / W) | In Minutes |
|---|---|---|---|
| Low (2835) | 24 W | 1.85 hr | 1 hr 51 min |
| Medium (COB) | 48 W | 0.93 hr | 56 min |
| High (5050) | 70 W | 0.63 hr | 38 min |
| Ultra (5630) | 88 W | 0.50 hr | 30 min |
Verify the low-density row: 44.4 / 24 = 1.85 hr, and 1.85 x 60 = 111 minutes = 1 hour 51 minutes. The ultra row: 44.4 / 88 = 0.505 hr, and 0.505 x 60 = 30 minutes. Brightness and runtime trade off directly -- the 2835 strip lasts almost 4x as long as the 5630 because it draws about a quarter of the power.
These runtimes assume full-brightness white. Dimming a 48 W COB strip to 50% pulls roughly 24 W, which doubles its runtime to about 1 hour 51 minutes -- the same as the low-density strip at full output.
Runtime by Battery Capacity (Fixed 24 W Strip)
Flip the variable: hold the strip at a low-density 24 W and scale the battery. Each raw Wh is (mAh / 1000) x 3.7, each usable Wh is raw x 0.80, and runtime is usable Wh / 24 W.
| Battery | Raw Wh (mAh x 3.7) | Usable Wh (x 0.80) | Runtime (Wh / 24 W) |
|---|---|---|---|
| 5,000 mAh | 18.5 Wh | 14.8 Wh | 0.62 hr (37 min) |
| 10,000 mAh | 37.0 Wh | 29.6 Wh | 1.23 hr (74 min) |
| 15,000 mAh | 55.5 Wh | 44.4 Wh | 1.85 hr (1 hr 51 min) |
| 20,000 mAh | 74.0 Wh | 59.2 Wh | 2.47 hr (2 hr 28 min) |
| 26,800 mAh | 99.2 Wh | 79.3 Wh | 3.30 hr (3 hr 18 min) |
The 15,000 mAh row reconciles with the density table exactly: 55.5 raw, 44.4 usable, 44.4 / 24 = 1.85 hr. Notice that 26,800 mAh is the largest bank most airlines allow -- its 99.2 Wh raw rating sits just under the 100 Wh TSA carry-on limit -- so it is the practical ceiling for portable strip power.
Tip
To roughly double runtime without a bigger battery, cut strip wattage: pick a lower-density reel, run a single color instead of full white, or dim to 50%. Each move is a direct multiplier on the runtime numbers above, since runtime is just usable Wh divided by watts.
Worked Example: 16 ft Strip on a 15,000 mAh Bank
Here is the full chain end to end, the way the calculator runs it internally:
- Strip: 16 ft low-density 2835 at 1.5 W/ft.
- Total watts: 1.5 x 16 = 24 W.
- Battery raw energy: 15 Ah x 3.7 V = 55.5 Wh.
- Usable energy: 55.5 x 0.80 = 44.4 Wh.
- Runtime: 44.4 / 24 = 1.85 hours = 1 hour 51 minutes.
Swap only the strip to a 48 W COB reel and one number changes: 44.4 / 48 = 0.92 hr = 55 minutes. Swap only the battery to a 26,800 mAh bank and instead: 99.2 x 0.80 = 79.3 Wh, then 79.3 / 24 = 3.30 hr = 3 hours 18 minutes. Every scenario is one division once you have usable Wh and strip watts.
If you also want the wall-power running cost rather than battery life, a 24 W strip for 6 hours a day at $0.12/kWh costs (24 / 1000) x 6 x 30 x 0.12 = $0.52 a month -- check your own rate with the Electricity Cost Calculator. For longer hard-wired runs where voltage drop matters, the Wire Gauge Calculator sizes the feed wire, and the Power Supply Calculator confirms adapter headroom.
Common Mistakes Sizing USB-C LED Strip Power
The math is simple, but the same errors show up over and over.
- Treating mAh as energy. A 15,000 mAh bank is not "15,000 units" of anything useful until you multiply by 3.7 V to get 55.5 Wh. Two banks with the same mAh but different cell voltages hold different energy.
- Forgetting the boost loss. Dividing raw 55.5 Wh by strip watts overstates runtime by about 25%. Always apply the ~80% usable factor first.
- Exceeding the USB-C port limit. A basic 5 V / 3 A port delivers only 15 W. A 48 W COB strip will dim and the bank may shut off -- you need a PD bank doing 9 V or 12 V for anything above ~24 W.
- Ignoring voltage drop at 16 ft. A 5 V strip loses brightness toward the far end over a 5 m run. Feed power to both ends, or use a 12 V/24 V strip stepped up through PD.
- Rating runtime at full white. Published wattage is the worst case. Real scenes draw less, so your actual battery life usually beats the table -- plan for the worst case and enjoy the margin.
For more whole-system planning math in the same area-and-power style, see how we calculate a lighting layout for a room, or how to plan a home AV setup where power and cabling stack the same way.
Frequently Asked Questions
how many watts does a 16 foot led strip powered by us. c need, and how ling would a 15,000mah battery tun them for
A 16-foot LED strip needs about 24 W (low-density 2835), 48 W (COB), or 70 W (high-density 5050) of USB-C power, and a 15,000 mAh battery -- 55.5 Wh raw, about 44 Wh usable at 80% efficiency -- runs the 24 W strip for 1.85 hours (1 hour 51 minutes), the 48 W strip for 0.92 hours (55 minutes), and the 70 W strip for 0.63 hours (38 minutes).
How many watts per foot does an LED strip use?
A standard LED strip uses about 1.5 watts per foot for low-density 2835 (4.8 W/m), 3.0 W/ft for COB (10 W/m), 4.4 W/ft for high-density 5050 (14.4 W/m), and 5.5 W/ft for ultra-bright 5630 (18 W/m), found by dividing the W/m rating by 3.281.
Can a USB-C power bank run a 16 ft LED strip?
A basic USB-C port supplies only 5 V / 3 A = 15 W, so it can run a 24 W low-density 16 ft strip only at reduced brightness; full brightness or any COB/5050 strip above 24 W needs a USB-C PD bank that negotiates 9 V or 12 V.
How do I convert 15,000 mAh to watt-hours?
Multiply amp-hours by the 3.7 V nominal cell voltage: 15 Ah x 3.7 V = 55.5 Wh raw, then multiply by about 0.80 for boost-converter and discharge losses to get roughly 44 Wh of usable energy at the USB-C output.
Why is my real LED strip runtime shorter than the math?
Real runtime falls short because the 3.7 V-to-5 V boost converter and the cells' unusable bottom charge waste about 20% of stored energy, so usable energy is roughly 44 Wh from a 55.5 Wh bank, and dividing 55.5 by watts (instead of 44) overestimates runtime by about 25%.
Does dimming an LED strip extend battery life?
Yes -- dimming roughly halves wattage at 50% brightness, so a 48 W COB strip dropping to about 24 W doubles its 15,000 mAh runtime from 55 minutes to 1 hour 51 minutes, because runtime equals usable watt-hours divided by watts.
What size battery runs a 16 ft LED strip the longest?
A 26,800 mAh bank (99.2 Wh raw, ~79 Wh usable) is the largest TSA carry-on-legal battery and runs a 24 W low-density 16 ft strip for about 3 hours 18 minutes, versus 1 hour 51 minutes from a 15,000 mAh bank.
Related Articles
- How to Calculate a Lighting Layout -- The same lumens-and-power planning method applied to recessed ceiling lights and grid spacing.
- Home AV Setup Calculator Data -- Power, cabling, and component planning for a media wall, where strip lighting and electronics share a circuit.
- Wall-to-Wall WiFi Coverage for a House -- Grid-and-coverage thinking for spreading devices across a floor plan, parallel to spreading power across a strip run.
Related Calculators
- LED Strip Calculator -- Enter strip length, type, and voltage to get total watts, amps, power-supply size, and monthly running cost instantly.
- Electricity Cost Calculator -- Estimate the monthly and yearly running cost of your strip at your local electricity rate.
- Power Supply Calculator -- Confirm the wall adapter or PD bank has enough headroom above the strip's draw.
- Wire Gauge Calculator -- Size the feed wire for long hard-wired runs so voltage drop doesn't dim the far end.
This article is for general educational purposes. LED strips and battery power involve real electrical and fire risk -- match voltage and current ratings, never exceed a port's rated output, and consult a qualified electrician for permanent wiring.
This article is provided for informational and educational purposes only. Content should not be considered professional financial, medical, legal, or other advice. Always consult a qualified professional before making important decisions. UseCalcPro is not responsible for any actions taken based on the information in this article.
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