Understanding the Compost Mix Calculator
Creating rich, biologically active compost requires more than just throwing kitchen scraps into a pile. A **compost mix calculator** helps you achieve the perfect Carbon-to-Nitrogen (C:N) ratio, which is the secret engine behind rapid, hot composting.
Why This Matters for Your Crops
The ideal C:N ratio for a compost pile is roughly 25-30 parts carbon to 1 part nitrogen. ‘Browns’ like dried leaves, straw, and cardboard provide the carbon (energy) for the microbes. ‘Greens’ like grass clippings, coffee grounds, and vegetable scraps provide the nitrogen (protein) needed for the microbes to multiply. If your pile has too much nitrogen, it will become an anaerobic, foul-smelling mess. Too much carbon, and the decomposition process will grind to a frustrating halt.
How to Use This Tool
Input the estimated weights or volumes of the brown and green materials you have on hand. The compost mix calculator will analyze your ratio and tell you exactly how much of a specific material you need to add to achieve the perfect 30:1 balance for rapid thermal breakdown.
Why Choose Our Compost Calculator?
Using a reliable compost calculator is essential for precision agriculture. Unlike manual guesswork, this compost calculator uses standardized formulas to provide accurate results every time. For more advanced resources, check out our full suite of hydroponic calculators or read more about agricultural standards on Wikipedia.
Quick Definition
EC (Electrical Conductivity) measures the total concentration of dissolved nutrients in your water, in mS/cm. TDS (Total Dissolved Solids) is the same measurement in ppm — the number changes based on your meter’s scale: ×500 (Hanna/Milwaukee), ×640 (European), or ×700 (Truncheon/Australia). This calculator supports all three scales plus CF, and checks 35 crop profiles across four growth stages.
EC / TDS / CF Calculator for Plants & Crops
Enter your meter reading, select your scale, choose your crop and growth stage, then instantly check if your nutrient solution is in range.
💧 Dilution Helper — How much water to add
⚠️ Add water in stages and recheck EC. Remove — litres first if tank space is limited.
📬 Get a Free EC & pH Management Cheat Sheet
We’ll send our complete EC, TDS & CF reference guide — crop tables, scale comparison, and stage-by-stage targets, ready to print.
📊 EC Range at a Glance — Vegetative Stage, Common Hydroponic Crops
Bar width represents the ideal EC window (mS/cm) during vegetative growth. Scale: 0–4 mS/cm.
Key Takeaways — What’s New in This Version
- All three PPM scales: 500 (Hanna/Milwaukee), 640 (European), 700 (Truncheon/Australia) — select the one that matches your meter.
- CF unit support: Enter readings in Conductivity Factor (CF = EC × 10) — common in UK and Australia.
- Growth stage targeting: Seedling, Vegetative, Fruiting/Flower, or Flush — each stage has different ideal EC targets.
- 35 crop profiles: Including Cannabis/Hemp, Strawberry, Microgreens, Watercress, Rosemary, Thyme, and more.
- Dilution helper: When EC is too high, the tool calculates exactly how much plain water to add to reach your target.
- Bidirectional conversion: Enter EC (any unit) or TDS (ppm) — converts both ways automatically.
- Pro Tip: Always measure your tap water EC first. If it reads 0.3 mS/cm, your nutrients only need to raise EC by (target − 0.3), not from zero.
What is EC and TDS — and why does the PPM scale matter?
This powerful EC to TDS converter is designed for accuracy. EC (Electrical Conductivity) measures how well your nutrient solution conducts electricity, which directly reflects the total concentration of dissolved mineral salts. TDS (Total Dissolved Solids) expresses the same measurement in parts per million (ppm). The two readings come from the same sensor — the difference is just the conversion factor applied.
This is where growers get confused: the same solution reads differently depending on which scale your meter uses. A solution at 1.6 mS/cm EC reads as 800 ppm on the 500 scale, 1,024 ppm on the 640 scale, and 1,120 ppm on the 700 scale. Always match your calculator and nutrient schedule to the same scale.
| PPM Scale | Formula | Common Meters | 1.5 mS/cm = |
|---|---|---|---|
| 500 Scale | ppm = EC × 500 | Hanna, Milwaukee, most US brands | 750 ppm |
| 640 Scale | ppm = EC × 640 | European standard, Bluelab | 960 ppm |
| 700 Scale | ppm = EC × 700 | Truncheon, Australia & UK | 1,050 ppm |
| CF | CF = EC × 10 | UK, Australia — older systems | 15 CF |
How to use this EC/TDS/CF calculator
- Select your PPM scale: Choose 500, 640, or 700 to match your meter. Hanna/Milwaukee = 500; most EU brands = 640; Truncheon = 700.
- Choose your EC unit: Toggle between mS/cm, µS/cm or CF. µS/cm values are 1,000× larger than mS/cm (1,500 µS/cm = 1.5 mS/cm).
- Search or select your crop: Type in the search box to filter the 35-crop dropdown.
- Select your growth stage: Seedling, Vegetative, Fruiting/Flower, or Flush. Seedlings need roughly half the strength of mature plants.
- Enter your EC or ppm reading: Enter whichever your meter shows. Leave the other field blank.
- Click Convert & Check: Results show EC, ppm, CF, and your crop-stage ideal range with a colour-coded status bar.
- Act on the result: Too low → add nutrients. Too high → use the dilution helper to see how many litres of plain water to add.
Ideal EC ranges by crop and growth stage
| Crop | Seedling (mS/cm) | Vegetative (mS/cm) | Fruiting/Flower | Flush |
|---|---|---|---|---|
| Lettuce | 0.6–0.8 | 1.2–1.8 | 1.6–2.0 | 0.5–0.8 |
| Tomato | 0.8–1.2 | 2.0–2.8 | 2.5–3.5 | 0.5–0.8 |
| Pepper / Chili | 0.8–1.2 | 2.0–3.0 | 2.5–3.5 | 0.5–0.8 |
| Cucumber | 0.6–1.0 | 1.7–2.5 | 2.0–3.0 | 0.5–0.8 |
| Basil | 0.4–0.6 | 1.0–1.6 | 1.4–1.8 | 0.4–0.6 |
| Spinach | 0.8–1.0 | 1.8–2.3 | 2.0–2.5 | 0.5–0.8 |
| Strawberry | 0.4–0.6 | 1.0–1.4 | 1.2–1.6 | 0.4–0.6 |
| Broccoli | 1.0–1.4 | 2.8–3.5 | 3.0–3.5 | 0.5–0.8 |
| Cannabis / Hemp | 0.4–0.8 | 1.2–2.0 | 1.6–2.4 | 0.5–0.8 |
| Microgreens | 0.5–0.8 | 0.8–1.2 | N/A | 0.4–0.6 |
EC and TDS problems — causes and fixes
| Problem | Cause | Fix |
|---|---|---|
| EC rising daily | Plants consuming water faster than nutrients | Top up with plain pH-adjusted water only. |
| EC falling daily | Heavy feeding — nutrients consumed faster than water | Top up with standard nutrient solution. Use the Nutrient Calculator to mix the right strength. |
| EC correct but plants yellowing | pH out of range — nutrients locked out | Check pH immediately. Correct pH before adjusting EC. |
| ppm readings don’t match supplier | Meter scale mismatch | Check which scale your meter uses vs. the nutrient brand. Always work in EC (mS/cm) to avoid scale issues. |
| EC varies with water temperature | EC is temperature-dependent | Quality meters auto-compensate to 25°C. Check at the same temperature each time. |
| Roots browning despite correct EC | Dissolved oxygen too low | Check water temperature (below 22°C). Increase aeration. |
EC monitoring: hydroponics vs soil
Hydroponic systems
EC is the most important daily measurement in hydroponics. Check EC every day during active growth and after any reservoir top-up. Always pair EC checks with pH checks — never adjust one without checking the other.
Soil and raised beds
Soil growers can measure EC in their runoff water to gauge nutrient build-up in the root zone. Runoff EC above 3.0 indicates salt accumulation — flush with clean water. Pair with the Soil NPK Calculator.
Frequently Asked Questions
Related gardening tools
EC management works best when combined with pH monitoring and accurate nutrient dosing. These tools complete the picture.
pH Calculator — always check pH alongside EC. Correct pH range is 5.5–6.5 for hydroponics.
Nutrient Calculator — calculate exact gram weights of nutrients to reach your EC target.
Water Volume Calculator — know your reservoir volume before mixing nutrients to EC.
VPD Calculator — vapour pressure deficit affects how fast plants uptake nutrients at any given EC.
Sources & References
- UniversityUniversity of Arizona CEAC — Hydroponic Lettuce Handbook, EC Management Guidelines. ceac.arizona.edu
- ExtensionUniversity of Vermont Extension — Nutrient Solution Management for Hydroponic Vegetable Production.
- RHSRoyal Horticultural Society (RHS) — Electrical conductivity and plant feeding: guidance for greenhouse crops. rhs.org.uk
- ResearchResh, H.M. (2012) — Hydroponic Food Production, 7th Ed. CRC Press.
- ExtensionCornell University Cooperative Extension — Water Quality for Greenhouse and Hydroponic Production, Bulletin 122.
- JournalHortScience — Jensen, M.H. & Collins, W.L. (1985). Hydroponic vegetable production. Horticultural Reviews, 7, 483–558.