How to Mix Weed Killer Concentrate | The Right Ratio For Your Sprayer

Mixing weed killer concentrate starts with reading the exact label on your product, because dilution rates vary by brand, target weed, and sprayer type — a universal ratio does not exist.

A single mistake in the sprayer can waste concentrate, damage your lawn, or leave weeds standing. The fix is straightforward once you know the one rule that applies to every bottle: the label is law. Below are the exact steps, what the rates actually look like across common brands, and the mistakes that cost homeowners more than they realize.

Why There Is No One-Size-Fits-All Ratio

Weed killer concentrate is not a single formula. Roundup Weed & Grass Killer Concentrate, for example, calls for 3 fluid ounces per gallon for easy weeds and 6 ounces per gallon for tough established ones — rates that double depending on what you are spraying. Roundup Super Concentrate, an older formulation in EPA documents, uses 1.5 to 2 ounces per gallon. Ortho WeedClear Lawn Weed Killer Concentrate specifies 1.5 or 3.0 ounces per gallon depending on your grass type. And BioAdvanced 365 uses 3.2 ounces per gallon. The only way to know your number is the label on the bottle you hold.

The Basic Step Sequence

Step 1: Read the label start to finish. Confirm the weed species, whether you are spot-treating or broadcasting, and whether the product is safe for your turf type — Ortho’s label, for instance, gives different rates for St. Augustinegrass versus hybrid bermudagrass.

Step 2: Fill the sprayer halfway with water first. Multiple herbicide guides recommend this because adding water first reduces foaming and splashing when the concentrate goes in. Never pour water directly into undiluted concentrate.

Step 3: Measure the concentrate precisely. Use the measuring device recommended on the label. Spectracide explicitly says to carefully measure and mix as directed and warns against using food utensils that will later return to kitchen use.

Step 4: Add concentrate to the water, then top off with remaining water. Seal the sprayer and shake or agitate until the mixture is uniform and cloudy — a settled concentrate-plus-water solution should look homogeneous before any trigger is pulled.

Step 5: Apply only at the labeled rate. Do not overapply or overspray onto non-target plants. Some labels tie the mix rate to a specific coverage area — for example, 300 square feet per batch — so calibrating your sprayer matters as much as measuring the dose.

Mixing Mistake That Wrecks Results

The most common error is guessing the dilution. Because “weed killer concentrate” sounds uniform, homeowners often use last year’s ratio on this year’s product — and the results are either weak kill or lawn damage. Using the wrong sprayer tank is the second: Roundup’s own guidance warns against galvanized or unlined steel sprayers unless stainless steel, because glyphosate can react with certain metals. Stick with plastic, fiberglass, aluminum, or stainless steel tanks.

Pouring concentrate first and adding water on top is another frequent misstep — it creates more foam and can splash concentrate onto your hands or clothes. The half-water-first method avoids that entirely. And never reuse measuring cups or spoons that have held herbicide; once they touch concentrate, they are not food-safe anymore.

If you are shopping for a product that fits your specific weed problem and lawn type, our tested roundup of grass weed killer concentrate options may help narrow the choice.

Herbicide Mix Rates At A Glance