DLI Calculation & Logging

Required tools

• PPFD measurement or validated time-series data
• photoperiod duration
• calculator or worksheet
• record sheet

Before starting

• Confirm PPFD units are micromoles per square meter per second.
• Confirm the light-on duration represented by the calculation.
• Decide whether a single representative PPFD or a time series is appropriate for the question.

Step 1

Record PPFD basis

Document the PPFD value, spatial average, or time-series source being used.

Record: Record value/source, units, measurement plane, and method.

Step 2

Record light duration

Document the actual daily light-on duration represented by the calculation.

Record: Record hours per day and schedule notes.

Step 3

Calculate

For constant PPFD, calculate DLI as PPFD × light seconds per day ÷ 1,000,000. For changing PPFD, integrate the time series instead of using an unsupported constant assumption.

Record: Record calculation method and resulting mol m⁻² d⁻¹.

Step 4

Check plausibility

Confirm the result uses the intended photoperiod and photon-flux basis and that no unit conversion was omitted.

Record: Record reviewer/check status when used operationally.

PPFD source and photoperiod are both documented.

The calculation converts seconds and micromoles to moles correctly.

DLI is labeled with mol m⁻² d⁻¹ rather than PPFD units.

DLI summarizes photon exposure over a day; it does not preserve the timing or short-term intensity pattern that produced the total.