Plant Care
- • Climate Control & VPD16
- • Disease & Pest Management14
- • Nutrient Solutions & EC34
- • Plant Health Monitoring7
EC / PPM / CF Converter Hub
One hub for the grow-room numbers games: convert EC (mS/cm), PPM on the 500 / 640 / 700 scales and CF in any direction, pick the scale your meter actually uses, compare any two nutrient formulas element-by-element and dose pH Up / pH Down for the exact tank volume.
Conductivity cross-scale
live
ppm
1260
Raw EC
1800
PPM on 500
900
PPM on 640
1152
PPM on 700
1260
Segments show how one EC reading lands on each scale — 500, 640 and 700. The headline PPM holds in the centre.
Inputs
9 parameters · live recalculation on every change
MS/CM
0.1mS/cm
1.8mS/cm default
4mS/cm
PH
3.5pH
6pH default
8.5pH
PH
3.5pH
5.8pH default
8.5pH
L
5L
200L default
5000L
Advanced Settings — Deterministic Corrections
Deterministic model
9 inputs · 8 outputs
Runs 100% in your browser
This is a deterministic model: the same inputs always produce the same outputs, calculated entirely in your browser with nothing sent to any server. It is a planning aid — not a quote, not a dosing instruction, and not a yield forecast. Treat every line as a working estimate and validate it against your own prices and measurements.
It models one system: One hub for the grow-room numbers games: convert EC (mS/cm), PPM on the 500 / 640 / 700 scales and CF in any direction, pick the scale your meter actually uses, compare any two nutrient formulas element-by-element and dose pH Up / pH Down for the exact tank volume.
What the EC / PPM / CF Converter Hub returns
The engine computes 8 outputs from your 9 inputs. The headline number is PPM (selected scale) (ppm), alongside PPM 500, PPM 640, PPM 700. Every output updates live as you change a parameter.
What it does not do
Outputs depend on the inputs and assumptions shown here. Confirm relevant measurements and local conditions before acting.
STEP 01
Enter the meter reading as EC in mS/cm — the only number you should actually trust from a conductivity pen.
STEP 02
Select the TDS scale printed on your meter: 500 NaCl, 640 KCl or 700 (USA 442). The hub converts all three every time.
STEP 03
Read PPM on your chosen scale plus CF and µS/cm simultaneously so any two pieces of gear can be reconciled.
STEP 04
Compare any two nutrient formulas element-by-element at the same EC to see where one pulls ahead.
STEP 05
For pH, enter current and target pH plus tank volume; the hub suggests the pH Down / pH Up dose for the medium.
STEP 06
Retest 30 minutes after any pH or feed change — the dose is a starting point, never the final word.
\text{PPM}_{700} = \text{EC} \,(\text{mS/cm}) \times 700
TDS on the USA 442 scale
\text{PPM}_{500} = \text{EC} \times 500
NaCl scale — typical of £/American hand-held meters
\text{CF} = \text{EC} \times 10
EC Factor — the Commonwealth grower scale
\text{\u00b5S/cm} = \text{mS/cm} \times 1000
Conductivity without the milli prefix
\text{mL} = V\,(\text{L}) \times |\Delta pH| \times k_{medium}
pH up/down dose for the tank volume and buffering factor
\Delta e_{i} = k_{i}^{A}\,\text{EC} - k_{i}^{B}\,\text{EC}
Elemental delta between two formulas at the running EC
PPM is a calculation the meter makes, not a physical measurement. Only EC is truly measured; the multiplier is a style choice your meter\u2019s firmware baked in.
Always match the scale to your nutrient charts. A 1.8 mS/cm solution reads 900 ppm on the 500 scale, 1260 ppm on the 700 scale, and both are correct.
EC drifts with solution temperature (~2%/°C). Calibrate in 1413 µS/cm buffer and let the reservoir settle before judging a feed.
pH Down liquid should be diluted 1:10 before dosing small tanks, and always distributed around the reservoir, never dumped in one spot.
- Blok, J. (2015). Nutrient Solutions in Hydroponics. Practical Hydroponics & Greenhouses.
- Hanna Instruments — EC/TDS conversion scales (European 640 KCl, Australian 700 442, American 500 NaCl).
This model combines the earlier Conversions-and-reference-hub, Nutrient-comparator, Ph-adjuster models.
Q1: Why does my meter read hundreds of PPM differently from the chart? ▾
Because PPM is not measured, it is calculated — the meter multiplies EC by its own conversion factor. European meters typically use 640 (KCl), Australian and many US meters use 700 (442), and cheap American pens use 500 (NaCl). The same 1.8 mS/cm solution reads 900, 1152 or 1260 ppm depending on the scale. Fix it by matching the TDS scale on the chart to the scale on your meter label — the Converter Hub shows all three at once.
Q2: What is CF and how does it relate to EC? ▾
CF (EC Factor) is the Commonwealth scale: simply mS/cm multiplied by 10. So 1.8 mS/cm equals 18 CF. Some old blue-print charts quote "CF" instead of EC; the hub converts every reading in both systems in real time.
Q3: How much pH Down should I add? ▾
Treat the output as a starting dose: roughly 0.05 mL per litre per full pH point in hydroponics, a little less in coco and less still in soil. For a 200 L tank dropping pH from 6.2 to 5.8 that is about 4 mL of concentrated pH Down. Dilute it 1:10 for safety, distribute it around the reservoir, then retest after 30 minutes — buffering agents in the water will make the real requirement differ.
Q4: Does temperature change EC readings? ▾
Yes — conductivity rises roughly 2% per degree Celsius. Meters with automatic temperature compensation (ATC) correct for this; manual meters need a correction factor. Always read after the reservoir has equilibrated to room temperature, and calibrate regularly with fresh 1413 µS/cm buffer solution.