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Hydroponics ppm chart
Most "hydroponics ppm chart" searches want one of two things: a way to convert an EC reading to ppm, or a ballpark ppm for their crop. Here are both. The catch worth knowing up front: ppm isn't a fundamental measurement — meters actually read EC (electrical conductivity) and multiply it by a factor to display ppm, and different brands use different factors.
EC to ppm conversion chart (500 & 700 scale)
The 500 scale is ppm = EC × 500 (Hanna, Bluelab); the 700 scale is ppm = EC × 700 (Truncheon, HM Digital). Same solution, two numbers — always check which scale your meter uses.
| EC (mS/cm) | ppm (500 scale) | ppm (700 scale) |
|---|---|---|
| 0.4 | 200 | 280 |
| 0.6 | 300 | 420 |
| 0.8 | 400 | 560 |
| 1.0 | 500 | 700 |
| 1.2 | 600 | 840 |
| 1.4 | 700 | 980 |
| 1.6 | 800 | 1120 |
| 1.8 | 900 | 1260 |
| 2.0 | 1000 | 1400 |
| 2.2 | 1100 | 1540 |
| 2.4 | 1200 | 1680 |
| 2.6 | 1300 | 1820 |
| 2.8 | 1400 | 1960 |
| 3.0 | 1500 | 2100 |
To go the other way, divide: ppm ÷ 500 (or ÷ 700) gives EC. Because EC is the source value, it's the more reliable target — the ppm columns are just conversions of it.
ppm chart by crop (quick reference)
Typical ppm ranges on the 500 scale, for a fast look-up. For the full stage-by-stage table with EC, both ppm scales, pH and sources, see the hydroponic nutrient chart by crop and stage.
| Crop | ppm (500 scale) | Source |
|---|---|---|
| Lettuce | 400–900 | Cornell CEA |
| Leafy greens (kale, chard, spinach) | 600–900 | Penn State |
| Herbs (basil, cilantro, parsley) | 700–900 | Penn State |
| Strawberry | 600–900 | UF/IFAS |
| Microgreens | 500–900 | Produce Grower |
| Tomato (seedling → fruit set) | 600–1400 | Penn State / UF/IFAS |
| Pepper | 900–1200 | Cornell CEA |
| Cucumber | 900–1200 | UF/IFAS |
To keep a printable copy, use your browser's Print → Save as PDF — both charts fit on one page to tape by the reservoir. Fruiting crops climb through the season; tomatoes especially, so see the tomato ppm & EC schedule by stage.
Subtract your source water. Tap and well water already carry 100–300 ppm of dissolved solids. Measure the water before adding nutrients and subtract it, or every target above reads high. This matters more than which ppm scale you pick.
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Gear this guide uses
A ppm chart is only useful with a meter you trust and nutrients to hit the number.
- Read EC and ppm with an EC / ppm meter — check whether it's a 500- or 700-scale model.
- Hit the target with hydroponic nutrients like MasterBlend or General Hydroponics.
- Calibrate the meter periodically with EC calibration solution so the ppm it shows is real.
Crop does the conversion and the targets
Crop reads in either ppm scale or EC, sets the target for your crop and stage from Cornell and Penn State data, and calculates salt or branded-nutrient weights for your reservoir — accounting for source-water ppm. Pay once, no subscription, works offline.
FAQ
What is a good ppm for hydroponics?
Depends on the crop: leafy greens and lettuce run lean (~400–900 ppm on the 500 scale), herbs and strawberries ~600–900, and fruiting crops like tomato, pepper and cucumber higher (~900–1400). Match it to the plant and stage.
How do I convert EC to ppm?
EC × 500 for the 500 scale, or × 700 for the 700 scale. EC 2.0 mS/cm = 1000 ppm (500) or 1400 ppm (700) — same solution, two numbers.
What ppm is too high?
Above a crop's range: high ppm stresses roots and, in fruiting crops, competes with calcium (tip burn, blossom-end rot). Most vegetables stay under ~1400 ppm on the 500 scale.
Sources
- Cornell CEA (Mattson & Lieth) — A Recipe for Hydroponic Success
- Penn State Extension — Hydroponics nutrient solutions
- UF/IFAS — hydroponic tomato, cucumber & strawberry nutrient guidance; Produce Grower — microgreens
Conversions are exact; crop ppm ranges are starting points — adjust to your cultivar, system, and measurements.