{"id":11510,"date":"2026-10-08T14:45:08","date_gmt":"2026-10-08T12:45:08","guid":{"rendered":"https:\/\/libolux.com\/blog\/how-many-led-grow-lights-by-room-size\/"},"modified":"2026-10-08T15:18:45","modified_gmt":"2026-10-08T13:18:45","slug":"how-many-led-grow-lights-by-room-size","status":"publish","type":"post","link":"https:\/\/libolux.com\/en\/blog\/how-many-led-grow-lights-by-room-size\/","title":{"rendered":"How many LED grow lights you need for your room size"},"content":{"rendered":"
Quick answer<\/span><\/p>\n

The rule is a single line: required PPF = target PPFD \u00d7 square metres<\/strong>. For flowering without CO\u2082 a sensible target is 800 \u00b5mol\/m\u00b2\/s, so a 1 \u00d7 1 m tent asks for about 800 \u00b5mol\/s and a 2.4 \u00d7 2.4 m room for about 4,600.<\/p>\n

With that number you can open any spec sheet and see whether the fixture gets there. Below is the table worked out for the most common sizes, with the model that fits and the monthly running cost.<\/p>\n<\/div>\n

<\/div>\n

The sum, before you open any catalogue<\/h2>\n

There are two ways to get a light purchase wrong: under-buying, and flowering never fills in; and over-buying, and you pay a bill that does not turn into harvest. The same multiplication avoids both.<\/p>\n

The sum<\/span><\/p>\n

PPF (\u00b5mol\/s) = target PPFD (\u00b5mol\/m\u00b2\/s) \u00d7 area (m\u00b2)<\/strong><\/p>\n

Starting targets: 200<\/strong> \u00b5mol\/m\u00b2\/s in propagation, 450<\/strong> in vegetative growth and 800<\/strong> in flowering without added CO\u2082. If you want to know where those numbers come from, they are explained in the PPFD and DLI guide.<\/p>\n<\/div>\n

Two honest warnings before the table. First: PPFD is never uniform, the centre always reads higher than the corners, so these figures are averages. Second: mounting height changes the result as much as the model does; a bar fixture usually works well between 40 and 60 cm above the canopy in flowering.<\/p>\n

Table by tent or room size<\/h2>\n

Worked out at an average of 800 \u00b5mol\/m\u00b2\/s, the flowering target without CO\u2082. If your room is vegetative only, divide the \u00b5mol\/s by roughly 1.8.<\/p>\n

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Fixtures by room size<\/p>\n

Flowering \u00b7 800 \u00b5mol\/m\u00b2\/s<\/span><\/header>\n

\n
\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Tent or room<\/th>\nArea<\/th>\nLight required<\/th>\nFixture that fits<\/th>\nAverage PPFD<\/th>\nPower<\/th>\nElectricity\/month<\/th>\n<\/tr>\n<\/thead>\n
0.6 \u00d7 0.6 m<\/td>\n0.36<\/b><\/td>\n288<\/b><\/td>\n1 \u00d7 120 W \u00b7 dim to 83 %<\/small><\/td>\n967<\/b><\/td>\n120<\/b> W<\/td>\n9<\/b> \u20ac<\/td>\n<\/tr>\n
0.8 \u00d7 0.8 m<\/td>\n0.64<\/b><\/td>\n512<\/b><\/td>\n1 \u00d7 240 W \u00b7 dim to 74 %<\/small><\/td>\n1,087<\/b><\/td>\n240<\/b> W<\/td>\n17<\/b> \u20ac<\/td>\n<\/tr>\n
1.0 \u00d7 1.0 m<\/td>\n1.00<\/b><\/td>\n800<\/b><\/td>\n1 \u00d7 240 W<\/td>\n696<\/b><\/td>\n240<\/b> W<\/td>\n17<\/b> \u20ac<\/td>\n<\/tr>\n
1.2 \u00d7 1.2 m<\/td>\n1.44<\/b><\/td>\n1,152<\/b><\/td>\n1 \u00d7 400 W<\/td>\n806<\/b><\/td>\n400<\/b> W<\/td>\n29<\/b> \u20ac<\/td>\n<\/tr>\n
1.5 \u00d7 1.5 m<\/td>\n2.25<\/b><\/td>\n1,800<\/b><\/td>\n1 \u00d7 630 W Master Control<\/td>\n812<\/b><\/td>\n630<\/b> W<\/td>\n45<\/b> \u20ac<\/td>\n<\/tr>\n
2.4 \u00d7 1.2 m<\/td>\n2.88<\/b><\/td>\n2,304<\/b><\/td>\n2 \u00d7 400 W<\/td>\n806<\/b><\/td>\n800<\/b> W<\/td>\n58<\/b> \u20ac<\/td>\n<\/tr>\n
2.0 \u00d7 2.0 m<\/td>\n4.00<\/b><\/td>\n3,200<\/b><\/td>\n3 \u00d7 400 W<\/td>\n870<\/b><\/td>\n1,200<\/b> W<\/td>\n86<\/b> \u20ac<\/td>\n<\/tr>\n
2.4 \u00d7 2.4 m<\/td>\n5.76<\/b><\/td>\n4,608<\/b><\/td>\n4 \u00d7 400 W<\/td>\n806<\/b><\/td>\n1,600<\/b> W<\/td>\n115<\/b> \u20ac<\/td>\n<\/tr>\n
3.0 \u00d7 3.0 m<\/td>\n9.00<\/b><\/td>\n7,200<\/b><\/td>\n4 \u00d7 630 W Master Control<\/td>\n812<\/b><\/td>\n2,520<\/b> W<\/td>\n181<\/b> \u20ac<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

Average PPFD across the whole area; the centre always reads above and the corners below. Running cost at 12 h\/day, 30 days and \u20ac0.20\/kWh. Where the fixture overshoots the target, the column shows the percentage to dim it to.<\/p>\n<\/div>\n<\/div>\n

The running-cost column assumes 12 hours of light, 30 days and \u20ac0.20\/kWh. Treat it as an order of magnitude and put your own tariff into the calculator below.<\/p>\n

Work it out with your exact measurements<\/h2>\n

Commercial tents are rectangular and real rooms are almost never square. Put in the metres you actually have and the stage you will be running:<\/p>\n

<\/div>\n

One big fixture or several small ones?<\/h2>\n

For the same total PPF, splitting into several units gives a flatter PPFD and less shadow in the corners \u2014 which is exactly where yield is lost. The trade-off is price per \u00b5mol, wiring, hanging points and more things that can fail.<\/p>\n