THC Detection Calculator
Answer a few quick questions — get personalized results backed by science.
Trusted by 9,000+ people every month — helping you make sense of a stressful situation, with clear answers instead of guesswork.
Created together with
Dr. Matthew Nuesse
DOT Certified Medical Examiner
Built on the science
Every estimate is based on peer-reviewed toxicology research, not guesswork.
Read the full methodology →
Know what to do next
Get matched to the right test kit for your exact timeline, based on your result.
About this calculator
What it estimates: a personalized urine THC detection window at two thresholds — Standard (50 ng/mL, the common workplace cutoff) and Confirmatory (15 ng/mL, a more sensitive lab-grade cutoff).
What it's based on: peer-reviewed toxicology research, reviewed by Dr. Matthew Nuesse, DOT Certified Medical Examiner.
What it doesn't do: it doesn't estimate blood, saliva, or hair detection windows, and it isn't a substitute for an actual test — individual results vary based on physiology, hydration, and metabolism.
Why we ask what we ask: each question — age, body type, usage frequency, duration of use, and lifestyle factors — directly affects how quickly THC clears your system. More accurate answers give a more personalized estimate.
Read the full methodology →*Your answers are stored securely, never shared with third parties, and used only for research purposes.
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⚠ Prolonged retention beyond this estimate has been documented in extreme chronic-use cases. Consider an at-home confirmatory test before relying on this range alone.
| Urine Test Cutoff | Estimated Window | Notes |
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Estimates are based on peer-reviewed toxicology research and population averages (Huestis 2007; Goodwin et al. 2008; SAMHSA cutoff guidelines). Individual results vary by physiology, hydration, and metabolism. This tool is informational only and is not medical or legal advice.
50 ng/mL and 15 ng/mL are standard federal screening and confirmation cutoffs (49 CFR §40.85).
