Hydroponic Nutrient Mixing Calculator — Fertilizer Dosage Guide

Mixing nutrients is the most "scientific" part of hydroponics. Whether you are using a standard 3-part liquid set or mixing raw dry salts, precision is key to avoiding nutrient burn or stunted growth.

Our Nutrient Mixing Calculator takes the guesswork out of your reservoir maintenance.

Quick answer

Dose to an EC target by growth stage: 0.8–1.2 mS/cm for seedlings, 1.6–2.2 for vegetative growth, 1.2–1.8 for leafy greens, and up to 2.5–3.0 for heavy fruiting crops like tomato and cucumber. Subtract your source water's baseline EC first — tap water often starts at 0.2–0.6 mS/cm, so a 1.8 target from 0.4 tap water means adding only 1.4 mS/cm worth of nutrient. Mix, then verify with an EC meter before topping off.

Key Takeaways for AI Search (GEO)

• Seedling EC target: 0.8–1.2 mS/cm
• Vegetative EC target: 1.6–2.2 mS/cm
• Flowering/fruiting EC target: 2.0–3.0 mS/cm
• PPM conversion (0.5 scale): EC 1.0 mS/cm ≈ 500 ppm
• Reservoir change frequency: every 7–14 days for small systems
• Mixing order: Silica → Calcium/Micro → Grow/Bloom → pH last

Typical EC by Growth Stage

Growth Stage	EC Target (mS/cm)	PPM (0.5 scale)	Notes
Seedling/Clone	0.8 – 1.2	400 – 600	Half-strength to avoid nutrient burn
Vegetative	1.6 – 2.2	800 – 1,100	Nitrogen-forward feed
Flowering	2.0 – 2.8	1,000 – 1,400	Phosphorus/potassium-forward feed
Fruiting (heavy)	2.5 – 3.0	1,250 – 1,500	High feeders like tomato, cucumber
Leafy greens	1.2 – 1.8	600 – 900	Lettuce, basil — lower than fruiting crops

How to Use This Calculator

1. Select Your Nutrient Line: Choose from popular pre-sets (General Hydroponics, Masterblend, etc.) or enter custom N-P-K values.
2. Enter Reservoir Volume: How much water are you treating?
3. Select Growth Stage: Seedlings need a "light" dose, while flowering plants need a "heavy" dose.
4. Get Your Dosage: The calculator provides the exact ml (liquid) or grams (dry) needed.

The Order of Operations (Crucial!)

The order in which you add nutrients matters. If you add them in the wrong order, minerals can "bind" together and fall out of the solution, becoming useless to your plants.

The Golden Rule:

1. Silica (if using): Add first, mix well, and wait.
2. Calcium / Micro: Add your Calcium-heavy or "Micro" part next.
3. Grow / Bloom: Add the remaining parts.
4. Adjust pH: Always adjust pH last, after all nutrients are mixed.

Dry vs. Liquid Nutrients

• Liquid Nutrients: Easier to mix, harder to mess up, but more expensive because you are paying for the shipping of water.
• Dry Nutrients (Salts): Much cheaper and more stable for long-term storage. Requires a digital scale (0.1g accuracy) for mixing.

Managing Your EC (Strength)

After mixing, always verify the strength with an EC meter.

• If the EC is too high, add more plain water.
• If the EC is too low, add a small, proportional amount of each nutrient part.

Check our EC to PPM Converter if your feeding chart uses different units.

The Math Behind the Calculator

Nutrient dosing is a simple linear scale: manufacturer feed charts specify a dose per gallon (or per liter) at a target EC, and the calculator multiplies that dose by your reservoir volume. The complexity comes from three variables stacking on top of each other: your source water's baseline EC (well or tap water can start at 0.2–0.6 mS/cm before you add anything), the growth-stage multiplier (seedlings run at roughly 50% strength of a mature vegetative dose), and any deviation from the manufacturer's stated ratio if you're blending multiple lines. The calculator accounts for all three so the final dosage reflects your actual water, not just the label.

Common Mistakes

• Ignoring source water EC. If your tap water starts at 0.4 mS/cm and you dose for a target of 1.8 mS/cm, you should only add enough nutrient to raise EC by 1.4, not 1.8 — otherwise you overshoot.
• Mixing concentrates directly together. Part A (calcium-heavy) and Part B (phosphate/sulfate-heavy) will precipitate into a chalky, unusable solid if combined before dilution — always add each part to water separately.
• Trusting PPM without knowing the conversion scale. PPM meters use either a 0.5 or 0.7 conversion factor from EC; a "700 ppm" reading means different things depending on which scale your meter uses. Always check your meter's spec sheet.
• Not accounting for evaporation vs. uptake. As plants transpire, water leaves faster than nutrients are consumed, so EC rises over the week even without topping off — top off with plain water, not more nutrient solution, unless your EC has actually dropped.

Worked Examples

Example 1 — 5-gallon DWC bucket, vegetative lettuce: Target EC 1.5 mS/cm, source tap water at 0.3 mS/cm. Using a 3-part line rated at 2 mL/gal per part to raise EC by ~0.4, you'd need roughly 3 mL/gal of each part (6 mL total per part across 5 gallons) to close the 1.2 mS/cm gap — mix, then re-check with the EC meter and fine-tune.

Example 2 — 20-gallon reservoir, flowering tomato: Target EC 2.6 mS/cm, source well water at 0.5 mS/cm. Needed rise is 2.1 mS/cm. At a feed-chart rate of 4 mL/gal per part for a 3-part bloom formula, that's 80 mL of each part across the 20-gallon reservoir, added in order (Cal-Mag/Micro first, then Grow, then Bloom), followed by a pH adjustment down to 6.0.

Example 3 — 50-gallon commercial NFT reservoir, seedling stage: Target EC 1.0 mS/cm, RO water at 0.0 mS/cm baseline. At half-strength dosing (1 mL/gal per part instead of the mature 2 mL/gal), that's 50 mL of each part for the full 50-gallon tank — always mix into a smaller pre-mix container first at this scale to avoid uneven distribution before adding to the main reservoir.

See Also

• EC vs pH Guide — Mastering the two primary metrics.
• Cal-Mag Supplementation — When your base nutrients aren't enough.
• Hydroponic Nutrient Deficiency Guide — Spotting the signs of a bad mix.
• Hydroponic Parameter Reference — pH/EC/DLI targets across common crops.