Fertigation Calculators
Work out how much fertilizer, chlorine or acid to inject through your irrigation system: how much product a target ppm and system flow require, what strength your stock tank needs for a fixed injector ratio, and how a titration test converts into an injection rate. Each calculator answers one question, shows its formula, and works in US or metric units.
Before you inject anything
Fertigation and chemigation move fertilizer, chlorine or acid through the same lines that feed your water supply. Every system injecting chemicals needs proper backflow prevention, and every injector needs to be rated for the chemical going through it.
Acid dose is never estimated from a pH reading alone — it has to come from a titration test on your actual water. Always add acid to water, never water to acid, wear the protective equipment the product label calls for, and keep acid and chlorine on separate injection points rather than mixing them in one tank. When a calculator's result affects worker or crop safety, treat it as a starting point and confirm against your product label and local regulations.
Which fertigation calculator do you need?
Find your question below. Each calculator does one job, so picking the right one gets you a precise answer.
| Your question | Use this calculator | How it works |
|---|---|---|
| How much fertilizer product do I need per acre or per 1,000 sq ft? | Fertigation Calculator | Target nutrient rate, fertilizer analysis and density set product amount per application. |
| What injector rate gives me a target ppm out in the field? | Fertilizer Injection Rate Calculator | Target ppm, system GPM and stock concentration set gal/hr, or reverse-solve delivered ppm. |
| My injector runs at a fixed ratio — how strong should my stock tank be? | Fertilizer Injector Ratio Calculator | Proportioner ratio and target ppm set fertilizer amount per gallon of stock solution. |
| What ppm of N, P or K is my tank mix actually delivering? | Fertilizer PPM Calculator | Product analysis and amount per gallon of solution convert to ppm, or reverse-solve the amount needed. |
| How much chlorine do I inject to hit a target free chlorine level? | Chlorine Injection Calculator | Target free chlorine, system flow and product strength set a continuous or shock injection rate. |
| How much acid do I inject to reach a target pH? | Acid Injection Calculator | Your titration test result and system flow set the injection rate — never estimated from pH alone. |
All fertigation calculators
Fertilizer dosing and ppm
Injectors and ratios
Fertigation and chemical injection safety basics
What university extension research says, in brief. Each calculator goes into detail and cites its sources.
Acid dose comes from titration, not from pH alone
Alabama Cooperative Extension System explains that a water sample's pH reading doesn't tell you how much acid a system needs, since buffering capacity varies between sources — titrating the actual water is the only reliable way to size an acid dose.
Always add acid to water, never water to acid
Alabama Cooperative Extension System lists this as the first safety rule for acid injection: pouring water into concentrated acid can make it splatter violently, so acid is always added to water instead.
Keep acid and chlorine on separate injection points
Alabama Cooperative Extension System notes that when acid is used to boost chlorine's effectiveness, it needs its own injection system upstream of the chlorine point rather than being combined into one tank.
Backflow prevention is required, not optional
University of Georgia Extension recommends that any system injecting fertilizer, acid or chlorine include backflow prevention equipment, since a drop in system pressure can otherwise pull the chemical mixture back into the water supply.
Manufacturer injector, tank and label specifications always take priority over these general figures. For related data, see the reference charts.
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Sources and review
This page and its calculators are reviewed by Daniel Reeves, PE, CID. Last reviewed . See our methodology and editorial policy, or report an error.
- Curtis, L.M. & Tyson, T.W. Alabama Cooperative Extension System. Acid Injection for System Maintenance (ANR-0652).
- Granberry, D.M., Harrison, K.A. & Kelley, W.T. UGA Cooperative Extension. Drip Chemigation: Injecting Fertilizer, Acid and Chlorine (B 1130).