L70 LED Lifetime Calculator

Calculate when an LED fixture will reach L70 (70% of initial lumen output) based on IES TM-21 lumen maintenance data. Find replacement schedules, lumen depreciation curves, and project-specific useful life.

LED Fixture Data (TM-21)

Rated L70 Hours

Initial Lumens 4000

Ambient Temperature 25°C

Drive Current vs Rated 100%

Installation

Hours per Day 12

Maintenance Factor (MF)

Target Lumen Threshold 70%

Lifetime Analysis

Rated L70 lifetime—

Temp-adjusted lifetime—

Drive current adjustment—

Effective useful life—

Years at 12h/day—

Lumens at year 5—

Lumens at year 10—

L70 replacement date—

Recommended MF lumen boost—

—

years useful

At hours/day

—

% at yr 5

Lumen output

—

% at yr 10

Lumen output

—

k hours adj.

Effective L70

Lumen Depreciation Curve

—

L90 Point

90% output

—

L80 Point

80% output

—

L70 Point

70% output

The calculators and tools on LightingCalc.lighting are provided for general guidance and informational purposes only. Results are estimates based on standard formulas and the values you enter — they do not constitute professional engineering, electrical, or architectural advice. Always verify calculations with a qualified professional before making decisions for any safety-critical, code-compliance, or commercial application. LightingCalc.lighting makes no representations or warranties as to the accuracy or completeness of any result, and accepts no liability for errors, omissions, or any outcomes arising from reliance on this information.