Medical & Other Health Calculators
Assess key health indicators with our free medical calculators. From kidney function and blood alcohol estimates to sleep optimization and life expectancy projections, these evidence-based tools help you understand important health metrics and make informed decisions about your wellbeing.
GFR Calculator
Estimate your glomerular filtration rate to assess kidney function from creatinine levels.
BAC Calculator
Estimate your blood alcohol concentration based on drinks consumed, weight, and time.
Life Expectancy Calculator
Estimate your life expectancy based on lifestyle factors, health habits, and demographics.
Smoking Cost Calculator
Calculate how much money you spend on smoking and how much you could save by quitting.
Sleep Calculator
Find the best bedtime or wake-up time based on sleep cycles for optimal rest.
How to Choose the Right Medical Calculator
Our medical calculators cover a range of health assessments. The GFR calculator is particularly important for anyone monitoring kidney health or managing conditions that affect renal function, such as diabetes or hypertension. It uses the CKD-EPI equation, which the National Kidney Foundation recommends as the standard for estimating kidney filtration rate.
The BAC calculator helps you understand how alcohol consumption affects your body based on your specific characteristics. While useful for awareness, it provides estimates only and should never be used to determine fitness to drive. The sleep calculator helps optimize your rest by aligning your schedule with natural 90-minute sleep cycles, which can improve how refreshed you feel upon waking.
The life expectancy and smoking cost calculators serve as motivational tools. By quantifying the health and financial impacts of lifestyle choices, they can help reinforce positive behavior changes. Remember that all these calculators provide estimates for educational purposes and should not replace professional medical evaluation.
Understanding Medical Health Assessments
Medical health assessments use established clinical formulas and epidemiological data to estimate various health indicators. While they cannot replace laboratory tests or clinical evaluation, they provide valuable screening information and health awareness.
Glomerular filtration rate (GFR) measures how well your kidneys filter waste from your blood. A normal GFR is above 90 mL/min/1.73m². The CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation, updated in 2021 to remove the race coefficient, estimates GFR from serum creatinine levels, age, and sex. GFR below 60 for three or more months indicates chronic kidney disease.
Blood alcohol concentration (BAC) is influenced by body weight, biological sex, the number and type of drinks consumed, and the time over which they are consumed. The liver metabolizes alcohol at an average rate of about 0.015 g/dL per hour. Legal driving limits vary by jurisdiction but are commonly 0.08 g/dL in the United States. Impairment begins well below the legal limit, with reaction time and judgment affected at BAC levels as low as 0.02 g/dL.
Sleep science shows that the average adult needs 7 to 9 hours of sleep per night, organized into 4 to 6 cycles of approximately 90 minutes each. Each cycle progresses through light sleep, deep sleep, and REM (rapid eye movement) sleep. Waking during deep sleep causes grogginess (sleep inertia), while waking at the end of a complete cycle leaves you feeling more alert. Consistent sleep and wake times help regulate your circadian rhythm for better overall sleep quality.
Frequently Asked Questions
What is a normal GFR level?
A normal GFR is 90 mL/min/1.73m2 or higher. GFR between 60 and 89 may indicate mild kidney function decrease, often related to aging. GFR between 30 and 59 indicates moderate chronic kidney disease, while GFR below 15 indicates kidney failure. The National Kidney Foundation recommends regular GFR testing for people with diabetes, hypertension, or a family history of kidney disease.
How accurate is a BAC calculator?
BAC calculators provide rough estimates based on the Widmark formula and average metabolism rates. Actual BAC can vary significantly due to food intake, medications, liver health, hydration, and genetic factors. These calculators should be used for educational awareness only and never to determine whether it is safe to drive. The only reliable way to measure BAC is with a calibrated breathalyzer or blood test.
How many hours of sleep do adults need?
The National Sleep Foundation recommends 7 to 9 hours of sleep per night for adults aged 18 to 64, and 7 to 8 hours for adults 65 and older. However, individual needs vary. Signs you are getting enough sleep include waking without an alarm, feeling alert during the day, and not needing caffeine to function. Consistently sleeping fewer than 6 hours is associated with increased health risks.
Can lifestyle changes really affect life expectancy?
Research consistently shows that key lifestyle factors significantly influence lifespan. Not smoking, maintaining a healthy weight, regular physical activity, moderate alcohol consumption, and a balanced diet are each associated with added years of life. A landmark study in the American Journal of Epidemiology found that adopting all five healthy habits could extend life expectancy by over a decade compared to adopting none.