Light Requirements Calculator

What it does

A light requirement calculator that sets a target DLI for a chosen crop and development stage and sizes the supplemental lighting needed to meet it. Per-stage DLI targets come from the VibeLux crop reference database.

When to use it

Use it to compare your current DLI with a crop's stage target and estimate the PPFD, hours and electricity cost needed to close the gap. The fruiting-truss demand term applies to tomato only.

How it calculates

• Target DLI = the crop's stage DLI. For tomato, add 0.2 mol/m²/day per truss × (plants per m² ÷ 3).
• Required PPFD = target DLI ÷ (16 h × 0.0036)
• Supplemental hours = (target DLI − current DLI) ÷ (required PPFD × 0.0036), capped at 20 h/day.
• Energy cost assumes an LED efficacy of 2.7 µmol/J × electricity cost. The J/cm²/day figure = DLI × 21.76 (PAR-energy equivalent).

What you enter

Crop

Development Stage

Number of Trusses(tomato only)

Plants per m²

Current DLI(mol/m²/day)

Electricity Cost($/kWh)

What you get

Target DLI(mol/m²/day)

PAR-energy equivalent(J/cm²/day)

Required PAR(μmol/m²/s)

Supplemental Light(hours/day)

Energy Cost($/m²/day)

Light Requirements by Stage(mol/m²/day)

40-Week Tomato Crop Cycle DLI(mol/m²/day)

Related calculators

• Light Recipes
• PPFD Calculator
• Solar DLI Calculator
• Spectrum Designer