THCFarmer.com
122,058 Members Log In Register
Log In Register
THCFarmer tools Water Free, no sign-up

pH, EC and PPM chart and converter

Convert between EC, µS/cm, CF and every common PPM scale, then check the pH and EC ranges growers here run. Most members feed lighter than the bottle says: around 1.0 to 1.5 EC through flower.

Checked Oct 20, 2026 Source: THCFarmer member consensus (threads 52240, 111731, 141284)
One reading on every scale Parallel scales converting EC from 0 to 3.0 into microsiemens, CF, and the 500, 640 and 700 PPM scales. A band marks the member range of 1.0 to 1.5 EC through flower, which reads 1000 to 1500 microsiemens, CF 10 to 15, 500 to 750 on the 500 scale, 640 to 960 on the 640 scale and 700 to 1050 on the 700 scale. FIG. 04 · ONE READING, SIX SCALES PPM DEPENDS ON YOUR METER Same water, every scale MEMBER RANGE, FLOWER EC mS/cm 0.0 0.5 1.0 1.5 2.0 2.5 3.0 µS/cm ×1000 0 500 1000 1500 2000 2500 3000 CF ×10 0 5 10 15 20 25 30 PPM 500 ×500 0 250 500 750 1000 1250 1500 PPM 640 ×640 0 320 640 960 1280 1600 1920 PPM 700 ×700 0 350 700 1050 1400 1750 2100 EVERY SCALE IS EC × A FIXED FACTOR RANGE: MEMBER CONSENSUS
01

EC and PPM converter

Type a reading from any meter

Not sure which PPM scale your meter uses? Check the manual for a 0.5, 0.65 (or 0.64) or 0.7 conversion factor, or switch it to EC.

EC (mS/cm) 1.4
µS/cm 1400
PPM 500 700
PPM 650 910
PPM 700 980
CF 14
How much should the nutrients add?
RO water is near 0.0. Tap water is often 0.2 to 0.6.
Use the stage table below.
Nutrients add 1.1 EC 550 PPM (500) · 715 PPM (650) · 770 PPM (700)
EC to PPM conversion chart
EC (mS/cm) µS/cm PPM 500 PPM 650 PPM 700 CF
0.2 200 100 130 140 2
0.4 400 200 260 280 4
0.6 600 300 390 420 6
0.8 800 400 520 560 8
1.0 1,000 500 650 700 10
1.2 1,200 600 780 840 12
1.4 1,400 700 910 980 14
1.6 1,600 800 1,040 1,120 16
1.8 1,800 900 1,170 1,260 18
2.0 2,000 1,000 1,300 1,400 20
2.2 2,200 1,100 1,430 1,540 22
2.4 2,400 1,200 1,560 1,680 24
2.6 2,600 1,300 1,690 1,820 26
02

pH by medium

Feed or reservoir pH, not runoff

Medium Sweet spot Workable range Notes
Soil 6.3 to 6.8 6.0 to 7.0 Soil buffers pH, so water in the low-to-mid 6s and let it ride. Test a slurry or runoff if leaves start showing lockout.
Coco 5.8 to 6.3 5.8 to 6.5 Members split between 5.8 and 6.0 to 6.3. Treat coco as something between hydro and soil, and correct only the extremes.
Hydro (DWC, RDWC, NFT) 5.7 to 6.1 5.5 to 6.3 Let pH drift slowly through the range rather than pinning one number, so every nutrient gets its window.
03

EC by stage

Total EC in the bucket, water included

Stage EC (mS/cm) PPM 500 PPM 700
Seedlings and fresh clones 0.4 to 0.8 200 to 400 280 to 560
Early veg 0.8 to 1.2 400 to 600 560 to 840
Late veg 1.0 to 1.4 500 to 700 700 to 980
Early flower (weeks 1 to 3) 1.2 to 1.6 600 to 800 840 to 1,120
Mid flower (weeks 4 to 6) 1.4 to 1.8 700 to 900 980 to 1,260
Late flower (week 7 on) 1.0 to 1.4 500 to 700 700 to 980

Treat the top of each range as a ceiling, not a goal. Start low, raise EC in small steps, and back off at the first burnt tips. Autoflowers and nutrient-sensitive strains usually want the bottom half of each range.

04

What growers here actually run

From the THCFarmer archive

  • Runs coco at 6.0 in veg and 6.2 to 6.3 in flower. Below 6.0 or above 6.5 is where problems start.

    Unit541 Read the post →

  • Found 5.5 to 5.8 too low in coco and perlite, and settled on 6.0 to 6.3.

    One drop Read the post →

  • Keeps EC at 1.0 to 1.5 and has pulled half-pound plants indoors at those numbers.

    MIMedGrower Read the post →

  • Rarely goes over 1.5 EC (750 PPM on the 500 scale).

    Dirtbag Read the post →

  • Above about 800 PPM is where nutrient-sensitive strains like Blueberry crosses and some Diesels start to suffer.

    cemchris Read the post →
05

Threads worth reading

Discussions this page draws on

06

Go deeper

Learn guides on THCFarmer

07

Common questions

What is the difference between EC and PPM?

EC is what your meter actually measures: how well the water conducts electricity, which rises with dissolved salts. PPM is an estimate calculated from EC using a conversion factor. Meters use a 0.5 factor (the 500 or NaCl scale), a 0.64 to 0.65 factor (the 650 scale) or a 0.7 factor (the 700 or 442 scale). The same 1.6 EC feed reads 800, 1040 or 1120 PPM depending on the meter.

Which PPM scale is my meter using?

Check the manual or the label for the conversion factor. If you can switch the meter to EC, do it and share EC numbers on the forum. EC means the same thing on every meter.

Should I count my tap water in the EC?

Yes. Your meter reads everything in the bucket. Measure your plain water first; if it reads 0.4 EC and your target is 1.4, the nutrients should add about 1.0.

Why do so many growers here feed lower than the bottle says?

Nutrient charts are written to sell product and assume ideal conditions. Members commonly run 50 to 75 percent of label strength and keep EC around 1.0 to 1.5 through flower, raising it only when the plant shows it wants more.

Still not sure? Ask the growers.

Post your numbers, medium and a photo. Members with years on this have answered thousands of these.

08

More grow tools

These numbers are starting points, not rules. Strains, water, medium and light all change what a plant wants, so watch your plants and adjust.

THCFarmer is not affiliated with any nutrient or equipment brand named on this page.

Back
Top Bottom