Formula Used
The calculator uses a statistical clearance model, not a laboratory instrument. It starts with an estimated initial residual score.
C0 = standard cutoff × frequency factor × exposure units × session factor × history factor × body factor × weight factor
R = C0 × 0.5^(days since last use / estimated half life)
Cutoff ratio = R / entered cutoff
Likelihood = 100 / (1 + e^(-1.65 × ln(cutoff ratio)))
Detection window = estimated half life × log2(C0 / cutoff)
Hair screening uses a sample length window model. It assumes about thirty days per centimeter, with a short entry lag.
How to Use This Calculator
Select the screening type first. Enter the days since last use, typical frequency, and exposure units. Use one exposure unit for low exposure, two for moderate exposure, and three or more for heavier exposure.
Enter body weight, body fat, metabolism profile, and the cutoff used by the test. For hair screening, enter sample length because longer samples represent a longer lookback window. Press calculate to view the estimate above the form.
Use CSV or PDF buttons after calculation to save your results. The estimate is educational only and should not be used as proof of any real screening outcome.
Understanding the Estimate
This calculator uses a simple statistical model for cannabis screening risk. It is not a medical test. It cannot know your exact metabolism, product strength, laboratory method, or sample handling. The result is a probability style estimate, not a promise.
Why Statistics Matter
Drug screening results vary because people vary. Frequency, body fat, exposure level, time since last use, and test type all change the final estimate. A single number can look precise, but real screening data has uncertainty. That is why the calculator gives a score, a ratio, and a range.
How the Model Works
The model starts with an estimated initial residual load. It then applies exponential decay. This is common in many clearance models. A half life means the remaining amount falls by half after one half life. The selected test cutoff is then compared with the remaining residual score.
Why Cutoffs Matter
A cutoff is a decision limit used by a screening method. Lower cutoffs are more sensitive. Higher cutoffs are less sensitive. The same residual score can produce different risk bands when the cutoff changes. This is why the calculator lets you enter the laboratory threshold directly for careful comparison.
Reading the Result
A low score means the model estimates a lower chance of a positive screen. A high score means the estimated residual level may still sit above the selected cutoff. The risk band should be read with caution. Laboratory confirmation, collection rules, and sample quality can change outcomes.
Good Use Cases
This tool is best for education, research planning, and statistical learning. It can help students see how assumptions change risk estimates. It can also help writers, analysts, and wellness educators explain uncertainty in screening models.
Important Limits
The calculator does not diagnose impairment. It does not replace professional advice. It does not guarantee any result. It also does not model masking, dilution, substitution, or tampering. Those actions can create legal, workplace, or medical problems.
Practical Interpretation
Use the output as a rough planning signal only. Compare several scenarios. Change one input at a time. This helps you see which factors drive the estimate. Keep notes on the assumptions used. Always follow workplace, legal, and clinical requirements when they apply.
FAQs
What does this calculator estimate?
It estimates a statistical likelihood score for a positive cannabis screening result. It uses exposure assumptions, test type, cutoff, and timing. It is educational and not a real laboratory result.
Is the result exact?
No. Human metabolism, collection rules, laboratory methods, and product strength vary widely. The result is a simplified model with uncertainty, not a guarantee.
Which test types are included?
The form includes urine, saliva, blood, and hair screening. Each option uses different assumptions. Hair uses a sample length window, while other tests use exponential decay.
Why does cutoff value matter?
A cutoff is the decision threshold used for screening. Lower cutoffs can increase sensitivity. Higher cutoffs can reduce the model likelihood for the same residual score.
What formula is used?
The main model uses exponential decay. It compares an estimated residual score with the entered cutoff. A logistic equation then converts that ratio into a likelihood score.
Can this confirm a pass or fail?
No. Only an actual qualified test can report a result. This tool gives an educational estimate and should not be treated as proof.
Does it model dilution or tampering?
No. The calculator does not model masking, dilution, substitution, or tampering. It also does not provide advice for bypassing screening rules.
Why include confidence level?
The confidence setting widens or narrows the estimated window range. It helps show uncertainty around the model rather than presenting one exact day.