Nutrient (PPM/EC) Calculator
Enter your measurement and choose the unit. The calculator will convert it to the other two scales automatically.
*Note: Conversions can vary depending on meter brand and calibration. The 500 scale is also sometimes called the TDS scale. The 700 scale is common in some regions outside the U.S.
What do “PPM” and “EC” mean?
PPM (Parts Per Million) measures the concentration of dissolved solids in a nutrient solution. EC (Electrical Conductivity) measures how well the solution conducts electricity, which correlates to the amount of dissolved salts (nutrients). PPM is essentially a converted reading of EC based on a specific scale (e.g., 500 or 700).
What is the difference between the 500 and 700 PPM scales?
Various manufacturers use different conversion factors:
– 500 Scale (TDS): 1 EC = 500 ppm
– 700 Scale: 1 EC = 700 ppm
So, if your meter is set to the 500 scale, a reading of 1.0 EC would be about 500 ppm. On the 700 scale, 1.0 EC is 700 ppm.
Tip: Always check which scale your meter uses to avoid confusion.
Why does my nutrient company list a PPM that doesn’t match my meter?
Not all meters and nutrient brands use the same conversion factor. Some nutrient brands may reference 500 scale, others 700 scale. If your meter is calibrated to a different scale than the one the nutrient chart assumes, your readings can look off. That’s where this calculator helps bridge the gap.
How do I use this calculator?
1. Enter your reading (e.g., 600 ppm or 1.2 EC).
2. Select the unit from the dropdown.
3. View the converted results in the other two scales.
It’s great for comparing your meter readings to a nutrient schedule that’s published in a different scale.
Can I use PPM/EC interchangeably with TDS?
TDS (Total Dissolved Solids) is often used as a general term, but it’s typically measured in ppm. EC is a direct measurement of electrical conductivity, which some argue is more accurate because it’s not tied to a single conversion factor. TDS or ppm is an estimate derived from EC. This calculator helps standardize those estimates.
Why are my actual grow results different from the chart’s recommended PPM/EC?
A variety of factors can influence nutrient uptake:
– Water quality and pH levels
– Environmental conditions (temperature, humidity, etc.)
– Strain genetics and growth stage
Use the recommended PPM/EC values as guidelines, then adjust based on how your plants respond.
What happens if my PPM/EC is too high or too low?
– Too High (Overfeeding): Risk of nutrient burn, leaf tips curling or turning brown, and potential salt buildup.
– Too Low (Underfeeding): Risk of slow growth, nutrient deficiencies, and overall weaker plants.
Do temperature and calibration affect meter readings?
Yes. Temperature can change water’s conductivity, and many EC/PPM meters use built-in temperature compensation. Calibration is also crucial—if your meter isn’t calibrated properly, readings may be off. Regularly calibrate using the correct solution recommended by the meter’s manufacturer.
Which scale is best for cannabis growing—500 or 700?
Neither is inherently “better.” The 500 scale is often seen in the U.S., while the 700 scale is more common in other regions. What matters most is consistency. If your nutrient schedule references 700 scale, try to use a meter that also displays 700 scale readings—or convert the values using this calculator.
Does organic growing require PPM/EC measurements?
Some purely organic growers don’t focus as heavily on PPM or EC, relying more on soil biology and slow-release amendments. However, many still measure runoff EC or leachate to track salt buildup or monitor pH. It all depends on your cultivation style.
How accurate is this calculator?
This calculator is based on the common 1 EC = 500 ppm (500 scale) and 1 EC = 700 ppm (700 scale) conversions. Different meters may have minor variations (e.g., 1 EC = 640 ppm). Always rely on your meter’s instructions for the most precise readings.
