THC Drug Test Calculator: How Long Can Weed Stay Detectable in Urine?

Explore approximate urine detection windows based on how frequently cannabis has been used, and learn how urine, oral fluid, blood, and hair tests differ. This is an educational comparison, not a prediction of when you will test negative.

Important: A drug test detects an analyte above a laboratory cutoff. Timing varies with dose, product, frequency, test type and sensitivity. A positive result can persist beyond an example window; no calculator can guarantee a negative test on a particular date.

THC urine detection calculator: choose a use pattern

Choose the description that best matches your pattern of use. These are broad examples, not individual clearance calculations.

How frequently have you used cannabis? Single use — one isolated occasion Moderate use — around four times weekly Daily use — regular daily use Long-term heavy use — sustained, heavy daily use

How long can THC be detected by different tests?

Urine

Usually tests for THC-COOH, an inactive metabolite. A frequently used screening cutoff in US federal workplace testing is 50 ng/mL, with a 15 ng/mL confirmation cutoff. Detection depends on the assay and use history.

Oral fluid (saliva)

Often detects THC associated with relatively recent use. Federal guidance describes detection for about 24–30 hours or longer after smoking; timing varies substantially.

Blood

Can test for THC and/or metabolites. Results depend strongly on what the laboratory measures, its cutoff, and the time since exposure. A dependable individual window cannot be inferred from frequency alone.

Hair

May reveal a longer history of exposure, commonly assessed over a roughly 90-day period for a typical scalp-hair sample. Results depend on sample length and test method, and hair testing is not a precise date-of-use tool.

What affects a THC drug test?

Frequency and amount of use: repeated exposure can extend urine metabolite detection.
What is measured: active THC and THC-COOH behave differently.
Cutoff and specimen: two laboratories may report different results for the same history.
Individual variation: metabolism and other biological differences make exact predictions unreliable.

Weight, age, exercise and hydration are not used as mathematical multipliers in this explorer. There is no sufficiently validated formula here to turn those inputs into a reliable negative-test date. Drinking extra water does not reliably speed THC elimination.

For more background, see what 50 ng/mL screening and 15 ng/mL confirmation mean, how drug tests work, and THC metabolism and storage.

Delta-8 THC drug test calculator: what can it tell you?

If you used delta-8 THC and are searching for a delta-8 drug test calculator, the key difference is what your laboratory tests for. Some urine cannabinoid screening tests also react to delta-8 THC metabolites. A screening reaction does not by itself tell you which THC isomer was present.

Can you use the calculator above for delta-8? You can explore the general impact of use frequency on delta-9 THC-COOH urine detection examples, but those example days are not validated delta-8 detection windows. The tool cannot estimate when delta-8 metabolites will disappear or predict whether a specific delta-8 product will trigger your test.

Does confirmation distinguish delta-8 from delta-9? It depends on the laboratory method and which compounds the test is designed to confirm. Some specific laboratory tests measure both delta-8 and delta-9 carboxy-THC separately. Other testing programs target particular metabolites; a screening result and a confirmed result must not be treated as interchangeable.

See our guide to THC drug-test screening and confirmation and urine testing cutoffs for more context.

Frequently asked questions about THC calculators

How long does weed stay in your system?

There is no single answer. The duration depends on the test type and what it measures. For urine tests, Mayo Clinic Laboratories provides approximate THC-COOH detection examples of up to 3 days after single use, up to 5 days with moderate use, up to 10 days with daily use and up to 30 days with chronic heavy use. Actual test results can differ, including beyond these example times.

Is a THC detox calculator scientifically reliable?

A calculator cannot establish when your body will be clear of THC metabolites or when you will pass a drug test. This tool compares published urine detection examples; it does not model an individual detoxification rate or promise a negative test.

What about delta-8 THC and drug tests?

Some cannabinoid urine screens also react to delta-8 metabolites, but laboratory confirmation depends on the specific analytes and test method. Our urine calculator uses published delta-9 THC-COOH examples, not validated delta-8 timelines. Read the delta-8 testing explanation above or our drug testing guide.

Can a THC calculator tell me when I will pass a test?

No. These educational examples are not guarantees. The only way to know a result for a particular test is the test itself.

Does drinking water clear THC faster?

Hydration can change urine concentration, but it does not reliably accelerate elimination of THC metabolites. Dilute samples may be handled differently by testing programs.

Why does the type of test matter?

Urine commonly detects metabolites, while oral fluid and blood testing may target parent THC or other compounds. Hair testing reflects a different exposure period.

Sources and methodology

The urine comparisons are based on Mayo Clinic Laboratories' approximate THC-COOH detection times: single use up to 3 days, moderate use up to 5 days, daily use up to 10 days, and chronic heavy use up to 30 days. These are illustrative upper endpoints reported in that reference, not universal limits. The calculator does not use unvalidated age, body weight, hydration or activity adjustments.

For educational purposes only; not medical, legal or employment-testing advice. Specific test results depend on the laboratory and specimen.