Cannabis nutrient schedule calculator
Tell the calculator what you grow, what you grow it in and how much your nutrient label says to use. You get a week-by-week plan with the EC to aim for, the pH range, the N-P-K focus and how many ml to mix into each feed.
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How the schedule is built
Every grow starts with two seedling weeks. Veg is split into an early and a late half, and flowering into the switch week, early flower, peak flower, two late weeks and a final week of plain water. Each stage gets an EC range and a share of your label dose. The ml per feed is that share multiplied by your label dose and the amount of water.
Starting points for coco and hydro (soil sits 0.2 lower, autoflowers at 80 percent):
- Seedling: EC 0.4 to 0.8, 25% of the label dose, N-P-K: 3-1-2
- Early veg: EC 0.8 to 1.2, 50% of the label dose, N-P-K: 3-1-2
- Late veg: EC 1.2 to 1.6, 75% of the label dose, N-P-K: 3-1-2
- Switch to flower: EC 1.4 to 1.8, 75% of the label dose, N-P-K: 1-3-3
- Early flower: EC 1.6 to 2.0, 100% of the label dose, N-P-K: 1-3-3
- Peak flower: EC 1.8 to 2.2, 100% of the label dose, N-P-K: 1-3-3
- Late flower: EC 1.2 to 1.6, 75% of the label dose, N-P-K: 0-5-5
- Flush: EC 0.0 to 0.4, 0% of the label dose, N-P-K: plain water
These numbers are a starting point, not a rule. Strains, lights and nutrient brands differ. Never go above the dose on your label. If leaf tips turn yellow or brown, check the pH first, then feed less.
The pH ranges and N-P-K ratios come from our guide Best nutrients for weed plants.
Frequently asked questions
What does a cannabis plant need in each growth stage?
In veg the plant builds leaves and stems, so it wants more nitrogen, around 3-1-2. Once it flowers it needs more phosphorus and potassium, around 1-3-3, and in late flower little or no nitrogen (around 0-5-5). The calculator shows the focus for every week.
What is the difference between EC and ppm?
EC is what your meter actually measures: how well the water conducts electricity, in mS/cm. ppm is an estimate made from that number, and meters use different factors. A 500-scale meter shows EC 1.0 as 500 ppm, a 700-scale meter as 700 ppm. Check which scale your meter uses before you compare.
Why does soil get a lower EC than coco or hydro?
Good potting soil already contains food, and it releases it slowly. Coco and hydro hold almost nothing, so everything the plant eats comes from your feed. That is why the soil targets in this calculator sit 0.2 lower.
Do autoflowers need less food?
Yes. Autoflowers stay smaller, grow faster and burn more easily. This calculator gives them 80 percent of the photoperiod EC and dose. Start low and only go up if the lower leaves turn pale.
Should I flush before harvest?
Most growers give plain, pH-adjusted water in the last week or two. In coco and hydro the flush can be short. In soil it takes longer for the leftover food to run out. The calculator plans one week of plain water at the end.
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