Shelf-Life (t90) Calculator
What is Shelf-Life (t90)?
Shelf-life (t90) is the time required for a drug to degrade to 90% of its original concentration. It is one of the most important parameters in pharmaceutical chemistry and drug formulation, as it determines the expiration date of a product.
Formula:
t90 = 0.105 / k
This equation is derived for first-order degradation reactions, which are the most common in pharmaceutical systems. The value 0.105 comes from logarithmic transformation of first-order kinetics equations.
Shelf-life is critical for ensuring drug safety, efficacy, and regulatory compliance. Pharmaceutical companies must determine t90 accurately to label expiration dates and ensure that drugs remain effective throughout their storage period.
Factors affecting shelf-life include temperature, pH, light exposure, and formulation. Higher temperatures typically increase degradation rates, reducing shelf-life.
In stability studies, the Arrhenius equation is often used along with t90 calculations to predict shelf-life under different storage conditions.
How to Use
- Enter rate constant (k)
- Click calculate
- Get instant shelf-life (t90)
Example
If k = 0.02 s⁻¹:
t90 = 0.105 / 0.02 = 5.25 s
This Shelf-Life Calculator is extremely useful for GPAT preparation, pharma students, and professionals working in formulation and stability studies.
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