Dry-Weight Rule Demystified: How the 0.3% Limit Works

Confused by “≤0.3% Δ9 THC on a dry-weight basis”? You’re not alone. This guide breaks down what the rule actually measures, how labs calculate it, and how it applies (differently) to flower, gummies, and drinks—without legalese or hype.

TL;DR

• Dry-weight basis means the percentage of delta-9 THC in a sample after moisture is removed.

• For hemp, federal law sets a limit of ≤0.3% Δ9 THC (dry weight); states can (and do) add their own rules.

• Flower is straightforward (low moisture after drying/cure). Finished goods (gummies/drinks) are trickier because moisture and serving size change the math—and some states regulate mg per serving/package instead of percent.

• Always read labels + COAs, and check state rules before you buy or ship.

1) What “dry-weight basis” actually means

When a lab tests material “on a dry-weight basis,” it first removes moisture from the sample to measure the concentration of Δ9 THC in the solids only. Reporting on a dry basis makes cannabis lab numbers comparable across batches that have different water content.

• Why it matters: Fresh plant material can look compliant if you count its water weight. Dry-weight reporting prevents that.

• What counts: Only the solid fraction of the sample—not the water.

2) How the 0.3% Limit Works (and where it gets nuanced)

• Federal baseline (hemp definition): ≤0.3% delta-9 THC on a dry-weight basis.

• State overlays: How the 0.3% Limit Works. Some states also enforce “total THC” rules for raw plant material (using a formula that includes THCA potential), or set caps in mg per serving/package for finished products (gummies, drinks).

• Bottom line: The federal line defines hemp, but retail legality of specific formats (and shipping) is state-specific. Always verify local rules.

3) Flower: the easy case

Dried, cured flower already has low moisture (typically ~10–13%). Labs report cannabinoids on a dry-weight basis, so the number you see for Δ9 THC is already aligned with the rule.

Example:

• Lab report for THCA flower lists Δ9 THC = 0.12% (dry) and THCA = 24% (plus a calculated “Total THC”).

• For hemp compliance, regulators look at Δ9 THC (0.12% here) and/or, in some states, Total THC.

• If your state enforces Δ9 only, 0.12% ≤ 0.3% → meets the federal Δ9 threshold (state “total THC” rules may differ).

Takeaway: For flower, compliance reading is relatively straightforward: check Δ9 % (dry) and know your state’s stance on total THC.

4) Gummies: percent vs milligrams

Gummies raise two questions:

1. Are regulators using percent by (dry) weight or mg limits?

2. What’s the product’s moisture content and net weight per piece?

Most gummies are labeled in mg of Δ9 per serving (e.g., 10 mg). But percent by dry weight is a different metric:

Worked example (illustrative math):

• One gummy weighs 4 g (4000 mg), of which water/volatiles might be ~15–25%.

• The gummy contains 10 mg Δ9.

• As-sold percent by net weight: 10 mg ÷ 4000 mg = 0.25% (under 0.3%).

• On a dry basis: suppose solids = 3.2 g (3200 mg) after removing moisture.

  • 10 mg ÷ 3200 mg = 0.3125% (dry weight) → over 0.3%.

Why you see debate online:

• Some jurisdictions judge finished goods by mg per serving/package (e.g., 10 mg per serving, 100 mg per package) and do not apply a dry-weight percentage to confections.

• Others scrutinize whether the dry-weight basis should apply beyond raw plant material. Rules differ.

Takeaway: For gummies, mg limits (where adopted) are the cleanest yardstick. If your state applies dry-weight logic to finished goods, moisture and piece weight can change the outcome.

5) Drinks: mostly water, same core question

A 12 oz (355 mL) beverage is ~355 g of liquid—nearly all water. If you compute percent by net weight, even 10 mg Δ9 looks tiny:

• As-sold percent by net weight: 10 mg ÷ 355,000 mg ≈ 0.0028% (far under 0.3%).

• On a dry basis: Most of a drink’s mass is water (removed in dry-weight testing), so the denominator collapses and the dry-basis percent rises. Depending on solids, a small mg amount can become >0.3% on a dry basis in strict interpretations.

Why states step in: Many set clear mg caps per serving/package for beverages to avoid dry-basis ambiguity in mostly-water products.

Takeaway: Always check state guidance for drinks—many regulate by mg, not percent.

6) How labs report (and why “Total THC” appears)

You’ll often see:

• Δ9 THC (% dry)

• THCA (% dry)

• Total THC (calculated): often (THCA × 0.877) + Δ9

That 0.877 factor accounts for CO₂ lost when THCA converts to Δ9 during heating (decarboxylation). Some states use Total THC for pre-harvest compliance in plants. For finished goods, rules vary.

Consumer tip: For hemp flower, ensure Δ9 % (dry) is ≤0.3% and check whether your state enforces Total THC. For edibles/drinks, look for clear mg per serving + mg per package and a batch-matched COA.

7) Common pitfalls (and how to avoid them)

1. Confusing mg and percent.

   • Percent is concentration; mg is quantity. A 0.25% gummy is not “0.25 mg”—it’s 0.25% of its weight.

2. Ignoring dry basis.

   • A product can be <0.3% by net weight but >0.3% on a dry basis if it’s moist or mostly water.

3. Using the wrong jurisdiction’s rule.

   • Don’t assume a federal definition equals state retail permission. Check current state rules.

4. Out-of-date COAs.

   • Use batch-matched COAs with dates and full panels (potency + safety).

5. No serving context.

   • Make sure labels clearly show mg per serving and servings per package—then compare to state caps.

8) Reading labels like a pro (quick checklist)

• Format first: flower vs edible vs drink—each is evaluated differently by regulators.

• Find Δ9 on the COA: % (dry) for raw material; mg per serving/package for finished goods.

• Look for “Total THC” on plant COAs; know if your state uses it.

• Serving math: mg per serving × servings per package = total mg.

• Safety panels: residual solvents (if extracts), pesticides, heavy metals, microbes.

• Batch match: COA batch ID should match your package.

9) What this means for shoppers in Texas (high-level)

• Expect active policy discussion around hemp-derived products.

• Retailers often highlight mg per serving/package on finished goods to align with consumer expectations and state practice.

• For flower, verify Δ9 % (dry) on the COA and understand how your locality treats Total THC.

• Laws evolve. Always review the latest state guidance before purchasing, shipping, or traveling with products.

10) FAQs

Q1: Why do some brands talk about mg while others use percent?Because percent is a concentration measure used in lab chemistry (great for flower), while mg is clearer for serving-based products like gummies and drinks.

Q2: Is a 10 mg gummy always compliant with the 0.3% rule?Not necessarily. Compliance depends on how your state regulates finished goods. Many use mg caps; dry-basis percent can look different, especially in moist products.

Q3: What’s the difference between Δ9 and “Total THC”?Δ9 is the active THC measured directly. “Total THC” estimates potential THC after decarboxylation from THCA (often THCA × 0.877 + Δ9). Some states consider Total THC for raw plant compliance.

Q4: Do drinks get special treatment?Often yes—because they’re mostly water. Many states rely on mg per serving/package to regulate beverages.

Q5: Are COAs required?Regimes vary, but batch-matched COAs are a best practice and commonly required. They also help you verify potency and safety.

Key takeaways

• Dry-weight basis removes water to standardize % numbers—critical for plant material.

• The 0.3% Δ9 limit defines hemp at the federal level, but states set retail rules for formats.

• Gummies/drinks are usually best understood in mg per serving/package; some states regulate exactly that.

• Always confirm with labels + COAs + current state guidance before you buy or ship.