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Glyphosate 41% Mixing Calculator: Percent Solutions Made Simple

Generic 41% glyphosate — Ranger Pro, Compare-N-Save, Eraser, and a dozen other labels — is the workhorse herbicide, and its labels speak a different language than consumer products: percent solutions for spot work and quarts per acre for broadcast. Both convert to ounces with one multiplication each, and this page does the math both ways — plus the two additions (surfactant and AMS) that generic labels expect and first-time users skip.

The one conversion to memorize: % × 1.28 = fl oz per gallon. A gallon is 128 oz, so 1% of it is 1.28 oz. Every percent-solution direction on the label resolves through that line.

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41% Glyphosate Calculator

Percent solution for spot spraying, or quarts-per-acre for broadcast work.

How the percent-solution system works

Professional and generic labels use percent-of-spray-volume because it scales to any tank: 2% is 2.56 oz in a gallon jug and 10.2 oz in a 4-gallon backpack, same strength either way. The typical 41% ladder:

Solution Oz per gallon Per 4-gal backpack Typical use
1% 1.28 5.1 oz Small annual weeds
1.5% 1.9 7.7 oz Mixed annuals + easy perennials
2% 2.6 10.2 oz General spot spraying standard
5% 6.4 25.6 oz Tough brush, vines
5–10% 6.4–12.8 — Cut-stump treatment (painted, not sprayed)

Common 41% label directions — your product's label is the law. Stronger isn't better on foliage: overdosed leaves burn before glyphosate translocates to roots, which is exactly the regrowth you were trying to prevent.

The two additions generic labels expect

Non-ionic surfactant — because generics often aren't fully loaded

Branded consumer Roundup ships with a full surfactant package; many generic 41% products don't, and their labels direct adding NIS — commonly 1–2 qt per 100 gallons, which works out to roughly 0.3–0.6 oz per gallon. Skipping it is the classic reason "the cheap stuff didn't work": spray beads up and rolls off waxy leaves instead of absorbing. Non-ionic surfactant↗ costs cents per tank.

Spray-grade AMS — the hard-water fix, added first

Calcium, magnesium, and iron in hard water bind glyphosate in the tank, deactivating part of the dose before it ever hits a weed — the classic well-water symptom is a mix that works in town and fails at the farm. Spray-grade ammonium sulfate↗ added to the water first (labels commonly allow 8.5–17 lbs per 100 gal, ≈1.5–2.7 oz dry weight per gallon) ties those minerals up before the glyphosate goes in. Mixing order is the whole trick: water → AMS → glyphosate → surfactant last.

FAQ

How much 41% glyphosate per gallon of water?

1% = 1.28 oz/gal, 2% = 2.6 oz/gal, 5% = 6.4 oz/gal — percent × 1.28. The calculator does any strength and tank size.

What percent solution should I use?

1% annuals, 1.5–2% general spot work, 5% brush, 5–10% painted on cut stumps. Stronger burns foliage before roots die — see the ladder.

Do I need surfactant with generic glyphosate?

Usually — many generics aren't fully surfactant-loaded and the label directs adding NIS at ~0.3–0.6 oz/gal. Details above.

Why add ammonium sulfate (AMS)?

Hard-water minerals deactivate glyphosate in the tank; AMS added to the water first prevents it. Matters most on well water.

How many quarts per acre?

Typically 1 qt/acre for small annuals up to 4–5 qt for tough perennials, in 10–20 GPA of water — set by your label's species table, not the maximum. The per-acre tab totals product and water.

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Important note

Rates here are common 41% label directions for planning; the label on your jug is the legal document and its rate tables, use sites, and precautions govern. Wear label-required PPE including chemical-resistant gloves↗. Affiliate links support the site at no extra cost to you.