🌿 Masterblend Fertilizer Calculator
Calculate exact Masterblend 4-18-38, Calcium Nitrate & Epsom Salt amounts for any tank or grow area
| Tank Size | 4-18-38 (g) | Cal-Nitrate (g) | Epsom Salt (g) | Target EC |
|---|---|---|---|---|
| 1 Gallon | 2.4 g | 4.8 g | 2.4 g | ~1.5 |
| 5 Gallons | 12 g | 24 g | 12 g | ~1.5 |
| 10 Gallons | 24 g | 48 g | 24 g | ~1.5 |
| 20 Gallons | 48 g | 96 g | 48 g | ~1.5 |
| 55 Gallons | 132 g | 264 g | 132 g | ~1.5 |
| 100 Gallons | 240 g | 480 g | 240 g | ~1.5 |
| Stage | EC Target | 4-18-38 Rate | Notes |
|---|---|---|---|
| Seedling / Clone | 0.8–1.2 | ~1.2 g/gal | Very dilute, sensitive roots |
| Early Veg | 1.2–1.5 | ~1.8 g/gal | Building root mass |
| Full Vegetative | 1.5–2.0 | 2.4 g/gal | Standard full strength |
| Transition / Pre-Flower | 1.8–2.2 | 2.8 g/gal | Increase EC gradually |
| Fruiting / Flowering | 2.0–2.5 | 3.2 g/gal | Peak nutrient demand |
| Heavy Fruiting | 2.5–3.0 | 3.6–4.0 g/gal | Experienced growers only |
| Final Flush | 0.0–0.5 | 0 g/gal | Plain water or light rinse |
| Tank (L) | 4-18-38 (g) | Cal-Nitrate (g) | Epsom Salt (g) | Est. EC |
|---|---|---|---|---|
| 1 Liter | 0.63 g | 1.27 g | 0.63 g | ~1.5 |
| 5 Liters | 3.17 g | 6.34 g | 3.17 g | ~1.5 |
| 10 Liters | 6.34 g | 12.68 g | 6.34 g | ~1.5 |
| 20 Liters | 12.68 g | 25.36 g | 12.68 g | ~1.5 |
| 50 Liters | 31.7 g | 63.4 g | 31.7 g | ~1.5 |
| 100 Liters | 63.4 g | 126.8 g | 63.4 g | ~1.5 |
| Crop | Veg EC | Fruiting EC | 4-18-38 Rate |
|---|---|---|---|
| Tomatoes | 1.5–2.0 | 2.5–3.5 | 2.4–4.0 g/gal |
| Peppers | 1.5–2.0 | 2.0–2.8 | 2.4–3.2 g/gal |
| Leafy Greens | 0.8–1.5 | 1.2–1.8 | 1.2–2.0 g/gal |
| Cucumbers | 1.5–2.0 | 2.0–2.5 | 2.4–3.0 g/gal |
| Strawberries | 1.2–1.5 | 1.5–2.0 | 1.8–2.4 g/gal |
| Cannabis / Hemp | 1.0–1.6 | 1.6–2.4 | 1.5–3.0 g/gal |
| General Hydro | 1.2–1.8 | 1.8–2.4 | 2.4 g/gal |
Masterblend fertilizer forms part of a three-part system. It must combine with calcium nitrate and magnesium sulfate, that one also knows as Epsom salt. The usual ratio is 1:1:½, so equal amounts of Masterblend fertilizer and calcium nitrate, except half as much Epsom salt.
In a basic hydroponic setup, the mix ratios are made up of 12 grams of Masterblend 4-18-38, 12 grams of calcium nitrate and 6 grams of Epsom salt for 5 gallons of water. That matches to around 2 spoons of Masterblend fertilizer and between 1.5 and 2 spoons of Epsom salt. To mix it, follow this sequence.
How to Mix Masterblend Fertilizer for Hydroponics
Add first the Masterblend fertilizer in water later add the Epsom salt, and lastly the calcium nitrate. Do not mix the ingredients together before putting them in the water. Each of them dissolves separate.
When one mixes the solution according to the advised ratio, it reaches around 1.6 EC, what matches to about 800 ppm according to the 500-scale. Some otehr mix one lands at 600 ppm or 1.2 EC. The liquid has a pleasant clear shade, and it does not smell.
One pound of Masterblend fertilizer stores around 453 grams. With 12 grams for 5 gallons, one pound gives roughly 189 gallons of nutrient solution. Every set prepares around 180 to 190 gallons.
A typical 25-pound set carries ten pounds of Masterblend fertilizer, ten pounds of calcium nitrate and five pounds of Epsom salt. One pound from the whole set causes around 90 gallons of solution for growing phase and 56 gallons four fruiting or flowering phase. For a smaller version, 5 pounds of Masterblend fertilizer combine with 5 pounds of calcium nitrate and 2.5 pounds of Epsom salt, what forms a 12.5-pound set.
There is also a focused mode. The formula Masterblend fertilizer for tomatoes and vegetables 4-18-38 dissolves in pure water with low TDS in one pound of fertilizer per gallon of water. Later one adds magnesium sulfate in 0.6 pounds per gallon.
For ground farming, after everything is mixed, one can use the solution in one quart per square foot of ground. For tomatoes, peppers, melons, squash and other big plants, one cup of solution per plant each one to two weeks works well. The fertilizer works also for outdoor use, not only for hydroponic systems.
Online there are calculators, that help to guess, how much Masterblend fertilizer you need for different sizes of bins; that is very handy for the Kratky method, where one uses various containers. Masterblend International for 35 years is a big maker of fertilizers in United States, serving professional growers and landscape caretakers around the world. They offer also a balanced 20-20-20 formula anda granular 10-20-10 variant in 50-pound bags.
