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LED Strip Calculator

Size your power supply and plan LED strip installation

Power Supply

90W

Amps

7.5A

$/Month

$1.52

Power Supply Needed

90W

7.5A @ 12V

Watts

70

Lumens

4389

Runs

1

Running Cost

Daily Energy0.42 kWh
Monthly Cost$1.52

What You'll Need

Klein Tools MM400 Digital Multimeter

Klein Tools MM400 Digital Multimeter

$28-$384.7
View on Amazon

Fluke T5-600 Voltage Continuity Current Tester

$145-$1604.8
View on Amazon
HUANCHAIN 50ft 12/3 Heavy Duty Outdoor Extension Cord

HUANCHAIN 50ft 12/3 Heavy Duty Outdoor Extension Cord

$25-$354.5
View on Amazon
HANYCONY Surge Protector Power Strip 8 Outlets 4 USB

HANYCONY Surge Protector Power Strip 8 Outlets 4 USB

$8-$144.8
View on Amazon
Jackery Portable Power Station Explorer 500 518Wh

Jackery Portable Power Station Explorer 500 518Wh

$250-$3504.5
View on Amazon
G40 LED Globe String Lights 100ft Outdoor 2-Pack

G40 LED Globe String Lights 100ft Outdoor 2-Pack

$35-$504.4
View on Amazon
Klein Tools MM400 Digital Multimeter

Klein Tools MM400 Digital Multimeter

$28-$384.7
View on Amazon

Fluke T5-600 Voltage Continuity Current Tester

$145-$1604.8
View on Amazon
HUANCHAIN 50ft 12/3 Heavy Duty Outdoor Extension Cord

HUANCHAIN 50ft 12/3 Heavy Duty Outdoor Extension Cord

$25-$354.5
View on Amazon
HANYCONY Surge Protector Power Strip 8 Outlets 4 USB

HANYCONY Surge Protector Power Strip 8 Outlets 4 USB

$8-$144.8
View on Amazon
Jackery Portable Power Station Explorer 500 518Wh

Jackery Portable Power Station Explorer 500 518Wh

$250-$3504.5
View on Amazon
G40 LED Globe String Lights 100ft Outdoor 2-Pack

G40 LED Globe String Lights 100ft Outdoor 2-Pack

$35-$504.4
View on Amazon

As an Amazon Associate, we earn from qualifying purchases.

Example Calculations

116 ft SMD 5050 under-cabinet strip

Inputs

Length16 ft (4.88m)
TypeSMD 5050 (14.4W/m)
Voltage12V
Usage6 hours/day

Result

Power Supply90W
Amps7.5A @ 12V
Monthly Cost$0.76

4.88m × 14.4W = 70.3W. ×1.2 = 84.3W. Round to 90W PSU. Cost: 0.070 × 6 × 30 × 0.12 = $1.51.

232 ft COB strip for cove lighting

Inputs

Length32 ft (9.75m)
TypeCOB (10W/m)
Voltage24V
Usage4 hours/day

Result

Power Supply120W
Amps5A @ 24V
Monthly Cost$1.40

9.75m × 10W = 97.5W. ×1.2 = 117W. Round to 120W PSU. Monthly: 0.098 × 4 × 30 × 0.12 = $1.41.

Frequently Asked Questions

Q

What size power supply do I need for LED strips?

Add up total watts (strip wattage/meter × length in meters), then add 20% headroom. A 5m strip of SMD 5050 at 14.4W/m needs 72W, so buy a 90W power supply.

  • Calculate total watts: W/m × total meters
  • Add 20% headroom: multiply by 1.2
  • Round up to next standard PSU size
  • Never run a power supply at 100% capacity
Strip TypeWatts/Meter5m TotalPSU Size
SMD 28354.8W24W30W
SMD 505014.4W72W90W
SMD 563018W90W120W
COB10W50W60W
Q

Should I use 12V or 24V LED strips?

24V strips allow longer runs with less voltage drop. Use 12V for short runs under 5m and 24V for anything longer. Both produce the same light output.

  • 12V: max 5m per run, cheaper controllers
  • 24V: max 10m per run, less voltage drop
  • 12V strips are more common and cheaper
  • 24V preferred for professional installations
Q

How much does it cost to run LED strips?

LED strips are very efficient. A 16-foot SMD 5050 strip draws about 70W and costs $0.50–$0.60/month running 6 hours/day at $0.12/kWh.

  • 5m SMD 5050: 72W = $0.78/month at 6h/day
  • 5m SMD 2835: 24W = $0.26/month at 6h/day
  • 5m COB strip: 50W = $0.54/month at 6h/day
  • Much cheaper than traditional light fixtures
Q

How do I avoid voltage drop in LED strips?

Never exceed 5m per run for 12V strips or 10m for 24V. For longer installations, inject power at both ends or use parallel runs from the power supply.

  • Voltage drop causes dimming at the far end
  • 12V: inject power every 5m
  • 24V: inject power every 10m
  • Use thicker wire (18 AWG+) for long cable runs

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Last Updated: Mar 19, 2026

This calculator is provided for informational and educational purposes only. Results are estimates and 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 calculator results.

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