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Conversions & reference

Hydroponic Conversions & Reference Hub

Convert EC to PPM (TDS), Celsius to Fahrenheit, liters to gallons, and kilograms to pounds — then check EC and temperature targets by crop. The quick reference every hydroponic and aeroponic grower keeps open.

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EC to PPM Converter (TDS)

Enter a value in either field. PPM = EC × scale. Most meters use 500, 640, or 700 — pick the one that matches your meter.

mS/cm  ·  = 1400 µS/cm
Parts per million as shown on your meter.

Temperature Converter

Nutrient solution temperature matters for dissolved oxygen and root health.

Volume Converter

Liters to US gallons and back — useful for reservoir sizing and dosing.

Mass Converter

Kilograms to pounds and back — handy for yield estimates and feeding schedules.

Quick Facts

The conversions growers search for every day, at a glance.

1 mS/cm = 1000 µS/cmSame reading, different unit.
1 gal = 3.785 LUS gallon, used for most reservoir math.
20°C = 68°FIdeal nutrient temperature range.
1 kg = 2.205 lbUsed for yield and dosing estimates.
EC × 700 = PPMExample: 1.4 mS/cm → 980 ppm.
PPM ÷ scale = ECExample: 700 ppm ÷ 500 = 1.4 mS/cm.

Reference Tables for Hydroponic Growers

Target EC and temperature values for common crops. Use the converter above to translate EC into your meter’s PPM scale.

EC & PPM targets by crop. PPM values are shown for the 500 and 700 scales (use the converter above to match your meter exactly).
CropEC (mS/cm)PPM @500PPM @700
Microgreens0.8–1.2400–600560–840
Lettuce0.8–1.2400–600560–840
Kale1.0–1.5500–750700–1050
Basil1.0–1.6500–800700–1120
Cannabis (veg)1.2–2.0600–1000840–1400
Strawberry1.5–2.0750–10001050–1400
Cucumber1.7–2.5850–12501190–1750
Bell pepper1.8–2.5900–12501260–1750
Cannabis (flower)1.8–2.6900–13001260–1820
Tomato2.0–3.51000–17501400–2450
Nutrient solution temperature targets. Warmer water holds less dissolved oxygen, which raises root-rot risk.
ScenarioTarget
Nutrient solution (most crops)18–22°C  (64–72°F)
Root zone ideal20–22°C  (68–72°F)
Cool-tolerant greens15–18°C  (59–64°F)
Warm-season fruiting crops21–25°C  (70–77°F)
Root-rot risk zoneAbove 24°C  (75°F)
Slowed nutrient uptakeBelow 15°C  (59°F)

Frequently Asked Questions

What is the difference between EC and PPM?

EC (electrical conductivity) is a direct measurement of how well your nutrient solution conducts electricity — a proxy for dissolved salts. PPM (parts per million) is a number your meter calculates from EC using a conversion factor. EC is the physical measurement; PPM is a scaled estimate.

How do I convert EC to PPM?

Multiply EC in mS/cm by your meter’s TDS scale: PPM = EC × scale. For example, 1.4 mS/cm × 700 = 980 ppm, or × 500 = 700 ppm. The converter above does this for the 500, 640, and 700 scales.

Which TDS scale should I use — 500, 640, or 700?

Use whatever scale your meter is set to. Hanna and many US meters use 500; Bluelab supports 500 or 700; many Australian and European meters use 640 or 700. Check the meter manual — using the wrong scale gives readings off by up to 40%.

Why do two meters give different PPM readings for the same solution?

Because they use different TDS factors. One meter might show 700 ppm while another shows 500 ppm for identical nutrient solution. Always compare EC (mS/cm) between meters, not PPM, and stay consistent with one scale over time.

What EC should my nutrient solution be?

It depends on crop and growth stage. Leafy greens and microgreens run low (0.8–1.6 mS/cm), while fruiting crops like tomato and pepper run higher (2.0–3.5 mS/cm). Seedlings and clones want roughly half the strength. See the table above for per-crop ranges.

What temperature should my nutrient solution be?

Aim for 18–22°C (64–72°F). Above 24°C (75°F) dissolved oxygen drops sharply and root-rot risk climbs, especially in DWC and NFT. Below 15°C (59°F) nutrient uptake slows noticeably.

More tools & calculators

Round out your setup with the rest of the toolkit.

Hydro Doctor

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Nutrient Calculator

Mix accurate nutrient solutions for your reservoir

Water Efficiency Calculator

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Plant Selection Tool

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Mist Timer Calculator

Dial in on/off misting cycles

Yield Calculator

Estimate your expected harvest

Grow Light Calculator

Find your PPFD and daily light integral

Cost & ROI Calculator

See when your setup pays for itself

VPD Calculator

Balance temperature and humidity

Looking for something else?

Browse every calculator and tool MistCulture has for hydroponic and aeroponic growers.

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Disclaimer: Target values are general guidelines — actual needs vary by cultivar, environment, and growth stage. © MistCulture.com

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