Free fertilizer calculator — pick your product, get its exact rates
Stop guessing at "a scoop per gallon." Choose any Greenway Biotech water-soluble fertilizer below and the calculator loads that product's approved application methods — hydroponic reservoir with live NPK ppm, soil drench, foliar spray, containers and pots, or dry garden application. Enter your reservoir size, pot count, or bed area and get the exact amount in grams and teaspoons.
Because we manufacture these fertilizers at our Madera, California facility, the methods and rates shown for each product come straight from our label data — the same guaranteed analyses that are CDFA registered and third-party tested for heavy metals. If a method isn't shown for a product, that product isn't intended for it.
How to use this calculator
Start with the product — each fertilizer loads its own calculator showing only the application methods it's actually made for. A crop formula like Tomato 4-18-38 offers hydroponic, drench, foliar, and container feeding; Urea offers soil methods only; chelated micronutrients offer solution methods only. If you don't see a method listed for a product, that product isn't intended for it — that's the answer, not a missing feature.
For hydroponic growers, the reservoir mode shows the resulting nutrient concentration in ppm, and nitrogen-containing hydro products unlock a Target PPM mode that works backwards — tell it the ppm you want, and it tells you what to mix. PPM values are shown as elemental N, P, and K, the convention used in hydroponic recipes and extension guides; the calculator converts from the label's P₂O₅ and K₂O for you (× 0.436 and × 0.83).
The Containers & Pots mode sizes solution feeding by container: pick your pot size and count, and it calculates both the mixing rate and how much solution you'll need. Container plants leach nutrients faster than garden beds, so the guidance runs dilute-but-frequent rather than strong-and-rare.
Calculator questions
Why do different products show different application methods?
Because chemistry and intended use differ. Urea nitrogen needs soil biology to convert into plant-available forms, so it's a soil product — it isn't offered for hydroponic reservoirs or foliar spray. Chelated micronutrients are solution products used at very low rates, so they aren't offered for dry broadcast. The methods shown for each product match its label — that's the point of choosing the product first.
Why do hydroponic, drench, and foliar rates differ for the same product?
Each method delivers nutrients differently. A recirculating reservoir bathes roots continuously, so concentrations stay moderate and are managed by ppm. A soil drench is applied intermittently and buffered by the soil, so rates run higher. Foliar sprays contact leaf tissue directly, which can burn at drench-strength concentrations, so rates run lowest. The most common fertilizer mistake we see is applying a drench rate as a foliar spray.
What ppm should I target for my crop?
General starting points for nitrogen in recirculating hydroponics: lettuce and leafy greens 100–150 ppm N; tomatoes 150–200 ppm N depending on stage; peppers 150–175 ppm N; cucumbers 150–180 ppm N; strawberries 100–150 ppm N. Seedlings take roughly half strength. These are starting points — light intensity, temperature, and variety all shift optimal targets. Our crop-specific formulas are pre-balanced so hitting the nitrogen target puts phosphorus and potassium in the right range automatically.
How often should I feed container plants?
More often, and more dilute, than garden beds. Containers hold a limited nutrient reserve and every watering leaches some of it out the drainage holes. A dilute solution at every second or third watering generally outperforms a strong monthly feeding, which risks salt buildup and root burn in the confined root zone. Flush containers with plain water monthly if you feed frequently, and always water until slight runoff so salts don't accumulate.
Are these rates specific to Greenway Biotech products?
Yes. Methods and rates are drawn from our label data and guaranteed analyses for products manufactured at our Madera, California facility. Other brands' products with similar NPK numbers may use different carriers, densities, or chelates, so their label rates can differ. Always follow the label on the product you're actually using.
Not sure which product you need in the first place? Take the 2-minute Fertilizer Finder quiz, browse all fertilizers, or start from what you're growing. Diagnosing a problem? Start with why plant leaves turn yellow.
