THC detection times vary more than almost any other substance because THC-COOH (the metabolite tested for) is fat-soluble and accumulates in adipose tissue. A single-use occasion may be detectable for 3–10 days in urine, while daily users can test positive for 30–90+ days after complete cessation. This makes frequency of use the single most important factor in predicting detection windows.
Urine tests detect THC-COOH, not active THC. The standard cutoff is 50 ng/mL for screening and 15 ng/mL for confirmation (GC-MS). Chronic users accumulate THC-COOH in fat cells, which is released slowly during fat metabolism — this is why exercise and weight loss can temporarily increase metabolite levels.
Body fat percentage is the second most important factor after frequency. THC-COOH is stored in fat tissue and released slowly. A 30% body fat individual may test positive significantly longer than a 15% body fat individual with identical usage patterns.
Blood tests detect active THC and are useful for determining recent use (within 1–3 days for occasional users). Saliva tests detect parent THC and are increasingly used in roadside testing with a 1–3 day window. Hair follicle tests can detect use for up to 90 days but may have false positives from environmental exposure.
Reach for this calculator when you need a standardised health metric to discuss with a healthcare provider or to use as a baseline for a fitness programme. The result gives you a number that carries more meaning than subjective assessments.
Many users apply adult health classifications to children and teenagers, which is incorrect. Paediatric norms for height, weight, BMI, and body composition are age-and-sex-specific. Use age-appropriate reference tools for anyone under 18.
A personal trainer uses the calculator with a new client to set a measurable starting point. Re-running the calculation at 4-week intervals provides an objective progress metric that supports motivation and programme adjustments.
THC Detection Estimation
Detection Days ≈ Base Window × (1 + Frequency Factor) × Body Fat Factor
Base window is 3–10 days for occasional use. Frequency factor adds 3–10× for daily users. Body fat factor adjusts ±20% based on body composition relative to average.
A daily cannabis user (3 months of use, 25% body fat) stops completely.
Result: This user should expect positive urine tests for approximately 5–12 weeks after stopping. Blood and saliva clear much faster (1–4 weeks). Hair testing will show a 90-day history regardless.
Single use: 3–10 days. Moderate use (few times/week): 10–20 days. Daily use: 30–60 days. Heavy chronic use: 60–90+ days. These are approximate ranges — individual variation is significant.
Yes, significantly. THC-COOH is fat-soluble and stored in adipose tissue. Higher body fat percentage extends detection times. Rapid weight loss can temporarily increase metabolite levels.
Extremely unlikely with standard cutoffs (50 ng/mL). Studies show that even extreme secondhand exposure in sealed rooms rarely produces levels above the screening threshold.
No reliable evidence supports detox products. Many work by dilution, which labs can detect via creatinine and specific gravity testing. Time is the only reliable clearance method.
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