Phq 9 Depression Score Calculator
Calculate your Phq 9 Depression Score by entering grades and credit hours. Get weighted GPA, letter grade equivalents, and improvement targets.
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Formula
The PHQ-9 scores nine DSM criteria for depression on a 0-3 scale based on frequency over the past two weeks. Total scores map to severity: 0-4 minimal, 5-9 mild, 10-14 moderate, 15-19 moderately severe, 20-27 severe.
Last reviewed: January 2026
Worked Examples
Example 1: Mild Depression Screening
Example 2: Treatment Response Monitoring
Background & Theory
The Phq 9 Depression Score Calculator applies the following established principles and formulas. Health and medicine calculators are grounded in validated physiological measurement methods established through decades of clinical research. Body Mass Index, or BMI, is calculated by dividing weight in kilograms by height in meters squared (kg/m²), a formula originating from Adolphe Quetelet's 19th-century statistical work and later codified by the WHO into standard classifications: underweight below 18.5, normal weight 18.5 to 24.9, overweight 25 to 29.9, and obese at 30 and above. Basal Metabolic Rate quantifies the minimum energy required to sustain life at rest. The Mifflin-St Jeor equation, published in 1990 and widely regarded as the most accurate for most adults, calculates BMR as (10 × weight in kg) + (6.25 × height in cm) − (5 × age) ± sex adjustment. The older Harris-Benedict equations, revised in 1984 by Roza and Shizgal, remain in common use. Total Daily Energy Expenditure is derived by multiplying BMR by a physical activity factor ranging from 1.2 for sedentary individuals to 1.9 for extremely active ones, following the methodology validated by doubly labeled water studies. Body fat percentage can be estimated without laboratory equipment using the U.S. Navy circumference method, which uses neck, waist, and hip measurements, or via BMI-derived equations adjusted for age and sex. The Jackson-Pollock skinfold method offers higher precision with calipers. Blood pressure classification, according to the American College of Cardiology and the 2017 ACC/AHA guidelines, defines normal as below 120/80 mmHg, elevated as 120 to 129 systolic, and hypertension stage 1 as 130 to 139 systolic or 80 to 89 diastolic. Target heart rate zones for aerobic exercise are derived from maximum heart rate estimates, most commonly using the formula 220 minus age in years, with moderate-intensity training typically defined as 50 to 70 percent of maximum heart rate and vigorous intensity at 70 to 85 percent, consistent with CDC and American Heart Association guidelines. These thresholds guide safe and effective cardiovascular conditioning.
History
The history behind the Phq 9 Depression Score Calculator traces back through the following developments. The history of health measurement stretches back to ancient Greece, where Hippocrates around 400 BCE laid the foundation for observational medicine by systematically recording patient symptoms, diet, and environment. His humoral theory, though scientifically superseded, established the principle that the body operates as an interconnected system subject to measurable imbalance. The transformation toward modern medicine accelerated in the 19th century. Louis Pasteur and Robert Koch developed germ theory in the 1860s and 1870s, identifying microorganisms as disease agents and enabling targeted interventions. Florence Nightingale, working during the Crimean War in the 1850s, introduced statistical analysis to nursing practice, demonstrating through data visualization that sanitation reduced mortality. Her work is foundational to evidence-based health measurement. The discovery of vitamins in the early 20th century, beginning with Casimir Funk's coinage of the term in 1912 and culminating in the isolation of vitamins A through K, created the field of nutritional science and gave rise to dietary reference intake frameworks. The World Health Organization, founded in 1948, subsequently established global standards for health metrics, disease classification through the International Classification of Diseases, and recommended daily allowances. The BMI as a clinical screening tool gained traction in the 1970s through Ancel Keys' large-scale epidemiological work, which validated Quetelet's index as a population-level obesity indicator. Through the 1980s and 1990s, the Framingham Heart Study produced landmark data linking cholesterol, blood pressure, and lifestyle factors to cardiovascular disease risk, directly shaping the numeric thresholds still used in health calculators. The evidence-based medicine movement, formalized by Gordon Guyatt and colleagues at McMaster University in the early 1990s, demanded that all health recommendations derive from systematically graded clinical evidence. The digital health era beginning in the 2000s brought these formulas to consumer devices, wearable sensors, and smartphone applications, expanding access to health self-monitoring on a global scale and enabling population-level data collection that continues to refine clinical reference ranges.
Frequently Asked Questions
Formula
PHQ-9 Total = Sum of Q1 through Q9 (each 0-3) | Range: 0-27
The PHQ-9 scores nine DSM criteria for depression on a 0-3 scale based on frequency over the past two weeks. Total scores map to severity: 0-4 minimal, 5-9 mild, 10-14 moderate, 15-19 moderately severe, 20-27 severe.
Worked Examples
Example 1: Mild Depression Screening
Problem: A patient scores: Q1=1, Q2=1, Q3=2, Q4=1, Q5=0, Q6=1, Q7=1, Q8=0, Q9=0. Interpret the result.
Solution: Total score: 1+1+2+1+0+1+1+0+0 = 7\nSeverity: Mild Depression (5-9 range)\nSomatic subscale: Q3+Q4+Q5+Q8 = 2+1+0+0 = 3/12\nCognitive subscale: Q1+Q2+Q6+Q7+Q9 = 1+1+1+1+0 = 4/15\nQ9 (self-harm): 0 — No safety concern\nRecommendation: Watchful waiting, repeat in 2-4 weeks
Result: PHQ-9 = 7 | Mild Depression | Watchful waiting recommended
Example 2: Treatment Response Monitoring
Problem: A patient on antidepressants had baseline PHQ-9 of 18. After 6 weeks, scores: Q1=1, Q2=1, Q3=1, Q4=2, Q5=1, Q6=1, Q7=0, Q8=1, Q9=0.
Solution: New total: 1+1+1+2+1+1+0+1+0 = 8\nBaseline: 18 (Moderately Severe)\nCurrent: 8 (Mild)\nChange: -10 points (>5 = clinically significant response)\nQ9 improved from prior positive to 0\nRecommendation: Treatment is working, continue current regimen
Result: PHQ-9 dropped from 18 to 8 | 10-point improvement | Treatment response confirmed
Frequently Asked Questions
What is the PHQ-9 and how is it used clinically?
The Patient Health Questionnaire-9 (PHQ-9) is a widely validated, self-administered screening tool for major depressive disorder. Developed by Drs. Robert Spitzer, Janet Williams, and Kurt Kroenke in 1999, it is based directly on the nine diagnostic criteria for major depression from the DSM (Diagnostic and Statistical Manual of Mental Disorders). Each question is scored from 0 to 3, yielding a total between 0 and 27. Clinicians use it for initial screening, monitoring treatment response over time, and measuring depression severity. It is used in primary care, mental health settings, research studies, and even occupational health assessments worldwide. The PHQ-9 takes approximately two minutes to complete.
What do the PHQ-9 score ranges mean?
The PHQ-9 score is interpreted across five severity ranges. A score of 0 to 4 indicates minimal depression symptoms that generally do not require treatment. Scores of 5 to 9 suggest mild depression where watchful waiting and lifestyle modifications may be appropriate. Moderate depression falls in the 10 to 14 range, where counseling or medication should be considered. Moderately severe depression, scored 15 to 19, typically warrants active treatment with antidepressants and psychotherapy. Severe depression is indicated by scores of 20 to 27 and calls for immediate treatment initiation, often combining medication with therapy and possibly specialist referral. A score of 10 or higher is commonly used as the clinical cutoff for major depression.
How accurate is the PHQ-9 for diagnosing depression?
The PHQ-9 has been extensively validated across diverse populations and settings. At the standard cutoff score of 10, it demonstrates a sensitivity of 88 percent and specificity of 88 percent for detecting major depressive disorder. This means it correctly identifies 88 percent of people with depression and correctly rules out 88 percent of people without depression. However, the PHQ-9 is a screening tool, not a diagnostic instrument. A positive screen should be followed by a clinical interview to confirm diagnosis, assess for comorbid conditions, evaluate suicide risk, and rule out other causes of symptoms such as thyroid disorders, medication side effects, or substance use. The PHQ-9 is most valuable when used longitudinally to track symptom changes over time.
How often should the PHQ-9 be administered for monitoring?
For treatment monitoring, the PHQ-9 should ideally be administered at each clinical visit, typically every two to four weeks during active treatment. A reduction of 5 or more points from the baseline score is considered a clinically meaningful response to treatment, while a score below 5 indicates remission. If starting antidepressant medication, reassessment at four to six weeks helps determine if the medication is effective. For patients in remission, quarterly reassessment during the continuation phase of treatment helps detect early relapse. In primary care screening settings, annual screening is recommended for adults by many clinical guidelines. Tracking scores over time provides an objective measure of progress that complements clinical observation and patient self-report.
Is my data stored or sent to a server?
No. All calculations run entirely in your browser using JavaScript. No data you enter is ever transmitted to any server or stored anywhere. Your inputs remain completely private.
Why might my result differ from another tool or reference?
Differences typically arise from rounding conventions, the specific version of a formula (for example, simple vs compound interest), or unit inconsistencies between inputs. Check that both tools are using the same formula variant and the same units. The References section links to the authoritative source behind the formula used here.
References
Reviewed by Rahul Singh, Health & Wellness Specialist · Editorial policy