If you’ve spent more than five minutes in hydroponics, you’ve hit the great nutrient confusion wall. Your meter says one thing, the bottle’s chart suggests another, and your plants just sit there looking judgmental. The problem usually isn’t the nutrients—it’s the translation. Electrical conductivity (EC) is the universal, unfiltered measurement of dissolved salts in your solution. PPM is simply a human-friendly conversion of that number, and it depends on scale. That’s exactly why this EC to PPM hydroponics calculator exists: to convert EC accurately using the 500, 640, or 700 scales, so you can feed with confidence instead of guesswork.

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How the EC to PPM Hydroponics Calculator Works

The calculator applies the correct conversion factor—500, 640, or 700—to your entered EC value. Because EC is the direct measurement your meter reads, it stays consistent across systems. PPM is the derived number that changes based on the scale used. By anchoring your feeding decisions to EC and using PPM as a reference, your nutrient strategy becomes accurate, repeatable, and free from scale-related confusion. You’re not just getting a number—you’re getting the right number for your system.

EC ↔ PPM
Hydroponics Calculator

Professional tool for precision nutrient management in hydroponic systems

Nutrient Concentration Calculator

500 Scale (TDS)

640 Scale (Hanna)

700 Scale (Truncheon)

Percent (%) to PPM

Electrical Conductivity (EC)

mS/cm

Parts Per Million (PPM)

PPM

0.0 2.5 5.0

EC vs PPM: Electrical Conductivity (EC) measures the solution's ability to conduct electricity, directly indicating nutrient concentration. PPM is a derived value that varies by conversion factor (500, 640, or 700 scale). EC is the more reliable measurement for hydroponics.

Crop & Growth Stage Intelligence

Select Crop Type

Select Growth Stage

Too Low Optimal Range Too High

Lettuce

EC: 0.8-1.2 mS/cm

Tomato

EC: 2.0-5.0 mS/cm

Strawberry

EC: 1.2-1.8 mS/cm

C-Plant (High Valued)

EC: 1.2-2.5 mS/cm

Frequently Asked Questions

What is EC (Electrical Conductivity)?

EC measures how well a solution conducts electricity. In hydroponics, it directly correlates with the concentration of dissolved nutrients (ions) in your water. Higher EC means more nutrients available to plants.

What is PPM (Parts Per Million)?

PPM is a unit of concentration that estimates the number of milligrams of nutrients per liter of water. It's calculated from EC using a conversion factor (500, 640, or 700 scale). PPM is less accurate than EC because the conversion factor varies by meter manufacturer.

Which scale should I use?

Use the 500 scale if you have a TDS (Total Dissolved Solids) meter from Hanna or Milwaukee. Use the 640 scale if your meter follows the common European conversion standard. Use the 700 scale for Truncheon meters or if you're in Australia. When in doubt, measure and work with EC directly.

Why is EC more reliable than PPM?

EC measures the actual electrical conductivity of the solution, which directly relates to ion concentration. PPM is a calculated value that depends on the conversion factor. Different manufacturers use different factors (500, 640, or 700 scale), making PPM readings inconsistent across meters.

Conversion Table

EC (mS/cm)	PPM (500 Scale)	PPM (640 Scale)	PPM (700 Scale)	Percent (%)
0.4	200 ppm	256 ppm	280 ppm	4000
0.8	400 ppm	512 ppm	560 ppm	8000
1.2	600 ppm	768 ppm	840 ppm	12000
1.6	800 ppm	1024 ppm	1120 ppm	16000
2.0	1000 ppm	1280 ppm	1400 ppm	20000

Note: EC is the true measurement. PPM values vary based on the 500, 640, or 700 scale.
Percent (%) values are calculated as PPM = Percent × 10,000.