Cannabis PPM Chart 2026: Week-by-Week EC & PPM Targets for Every Stage

The exact PPM and EC targets for cannabis from seedling to late flower — broken down by medium (soil, coco, hydro) with flush schedules and how to read a TDS meter correctly.

Why PPM & EC Are the Most Important Numbers in Your Grow

PPM (Parts Per Million) and EC (Electrical Conductivity) measure how much dissolved solids — nutrients — are in your water. Feed too little and plants starve. Feed too much and you get nutrient burn, salt lockout, or root damage that takes weeks to recover from.

Most growers who post "what's wrong with my plant?" photos in forums are either overfeeding or underfeeding. A $17 TDS/EC meter eliminates the guesswork entirely. The a basic pH & TDS combo meter gives you both readings in one tool.

Quick Unit Conversion:
EC 1.0 = ~500 PPM (using the 500 scale, common in the US)
EC 1.0 = ~700 PPM (using the 700 scale, common in Europe)

Always confirm which scale your meter uses. This guide uses the 500 scale (multiply EC × 500).

The Master PPM Chart: Every Stage, Every Medium

Stage Week Soil PPM Coco PPM Hydro PPM EC
Seedling1–2100–200250–350200–3000.4–0.6
Early Veg3–4300–500500–700400–6000.8–1.2
Late Veg5–6600–900800–1100700–10001.2–1.8
Early Flower1–3800–11001000–1300900–12001.6–2.2
Peak Flower4–61000–14001200–16001100–15002.0–2.8
Late Flower7–8700–1000900–1100800–10001.4–1.8
FlushFinal 1–20–500–500–500–0.1
Note: These are target ranges for the water going in (input PPM). Always measure and record both input and runoff.

Why PPM Targets Differ by Medium

Soil: Pre-amended soils (like a quality pre-amended potting soil) already contain nutrients. For the first 3–4 weeks, many soil growers feed plain pH'd water only and let the soil do the work. Start at the low end of the chart and increase based on plant response.

Coco Coir: Coco is an inert medium — it contains zero nutrients. Plants need feeding from day one of transplant, even seedlings. Coco also has a high cation exchange capacity, meaning it holds on to calcium and magnesium. Always add CalMag when growing in coco (aim for 150–200 PPM CalMag baseline before adding base nutrients).

Hydro (DWC/Recirculating): Roots are directly in the nutrient solution, so uptake is maximized. Plants are efficient — start at the lower end of the range. Monitor your reservoir PPM daily and top off with pH'd water (not fresh nutrient mix) as levels drop.

Runoff PPM: The Metric Most Growers Ignore

Measuring only your input PPM is like checking only your bank deposits and never your balance. Runoff PPM tells you what's actually happening in your root zone.

How to check runoff: Water normally, then collect the last cup of water that drains from the bottom of the pot. Measure its PPM and pH.

Interpreting runoff PPM:
Target runoff PPM: Aim for runoff that is within 200–400 PPM of your input. If you're feeding at 1,200 PPM, healthy runoff should be 1,200–1,600 PPM.

Reading Plant Signals: Too High vs. Too Low PPM

Your plants tell you when the PPM is off — if you know what to look for.

Signs of overfeeding (PPM too high):
Signs of underfeeding (PPM too low):
When in doubt, drop your PPM by 20–30% and observe for 3–5 days before making further changes. Plants respond slowly — patience is the skill.

When and How to Flush (Pre-Harvest PPM to Zero)

Flushing removes excess nutrient salts from your medium before harvest, allowing the plant to consume its internal reserves. This improves the smoothness and flavor of the final product.

When to flush:
How to flush soil/coco: Run 2–3x the pot volume through the medium with plain pH'd water (6.0–6.5 for soil, 5.8–6.0 for coco). Measure runoff PPM — you're aiming to get it below 200 PPM.

Signs your flush is working: Leaves will start to yellow and fade to yellow/purple as the plant pulls nutrients from its own tissue. This is exactly what you want in the final 7–10 days. A plant that stays dark green into harvest week didn't finish properly.

Frequently Asked Questions

What PPM should I use for cannabis in coco?

In coco coir, start seedlings at 250–350 PPM (EC 0.5–0.7), ramp to 800–1100 PPM in late veg (EC 1.6–2.0), and peak at 1200–1600 PPM during mid-flower (EC 2.2–2.8). Always add CalMag first to establish a 150–200 PPM base before adding your base nutrients.

What PPM is too high for cannabis?

Above 1,600–1,800 PPM (EC 3.0–3.5) is considered high even for heavy-feeding strains in peak flower. Most nutrient burn symptoms appear when plants are pushed above 1,600 PPM without being properly hardened to high feeding levels. Start low and increase gradually.

Should I pH before or after adding nutrients?

Always adjust pH after adding all nutrients to your water. Nutrients change the pH of your water, so pH'ing before you add them is wasted effort. Mix your nutrients first, check PPM, then adjust pH to your target range (6.0–7.0 for soil, 5.5–6.2 for coco/hydro).

How do I lower PPM in my reservoir?

To lower PPM in a DWC or recirculating hydro reservoir, simply add pH'd plain water to dilute the solution. Never dump and refill a reservoir unless PPM is severely out of range — it's a waste of nutrients and causes unnecessary pH swings.

Do autoflowers need lower PPM?

Yes. Autoflowers are generally more sensitive to nutrient concentration. Run autoflowers at 60–75% of the PPM targets listed for photoperiod plants. Start seedlings at 100–200 PPM and peak around 800–1,000 PPM in mid-flower rather than the 1,200–1,600 PPM used for photoperiods.

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