VAS: Visual Analogue Scale for Assessing Subjective Sensations

The Visual Analogue Scale (VAS) is a method for measuring things that are subjective and can't be directly "measured" in the usual sense - like pain, fatigue, shortness of breath, or overall well-being.

Instead of choosing from fixed categories ("low / medium / high"), the respondent marks their sensation on a continuous line, most often a 10 cm straight line:

• one end = no sensation at all (e.g., "no pain at all"),
• the other end = the maximum imaginable intensity (e.g., "worst possible pain").

VAS sits alongside other psychometric tools such as Likert Scales, Guttman Scales, Validity Scales and usability scales like SUS.

In digital surveys or health studies, you can implement VAS as a slider question in SurveyNinja, and combine it with both quantitative research and qualitative research methods.

Advantages of VAS

VAS has several strengths that explain its popularity in medicine, clinical research, psychology, UX and other fields.

1. Simplicity and versatility

The concept is easy to explain: "Put a mark where your current feeling is." This format works well for many types of sensations:

• pain,
• fatigue,
• anxiety or stress,
• hunger/satiety,
• overall well-being, etc.

In a digital survey tool like SurveyNinja, VAS can be implemented as a slider or drag-to-rate scale using visual scale question types, preserving the same idea in an online form.

2. High sensitivity to change

Ideal for longitudinal studies and treatment tracking. Because respondents aren't limited to 4–5 categories, VAS can detect small differences and gradual change over time - for example, the effect of a new treatment, medication, or training program.

3. Quantitative view of subjective sensations

A simple mark on a line turns into a numeric value, which makes it easy to:

• calculate averages and distributions,
• compare groups,
• track scores over time,
• run statistical tests.

VAS fits naturally into quantitative research while still capturing deeply subjective customer experience.

4. Non-verbal and language-light

Especially helpful in ethnographic research or multilingual contexts. VAS does not rely heavily on words. Once the endpoints are explained, the core action is visual and motor: "mark your spot." This is useful when:

• verbal description is hard (children, people with communication difficulties),
• there are language barriers,
• you work with multilingual populations.

5. Fewer language and cultural distortions

Because the scale is graphical, it reduces the risk that the wording of categories ("moderate", "severe", etc.) will be interpreted differently by different people or cultures. Only the anchors (end labels) need careful translation and adaptation.

6. Fast and convenient

VAS takes just a few seconds to complete, which is crucial in:

• busy clinics,
• longitudinal studies with frequent measurements,
• UX tests where you don't want to overload participants.

7. Less "central tendency" bias

In scales with discrete options, many respondents gravitate to the middle option ("3 out of 5", "neutral"). On VAS, there is no single "middle box" - people place their mark anywhere, which helps reduce this bias.

Of course, VAS is not perfect. It still relies on self-report, some participants may find it hard to decide where to mark, and interpretation can sometimes be tricky. But when designed and explained well, it remains a very valuable instrument in both research and practice.

Examples of VAS Usage

VAS is used wherever you need to measure subjective intensity. Here are some typical examples.

1. Pain assessment

The most common use-case: measuring pain intensity from "no pain" to "worst imaginable pain."

Doctors and researchers can:

• compare pain levels before and after treatment,
• evaluate effectiveness of analgesics,
• track recovery over days or weeks.

If you're doing a study, it's easy to combine VAS with other items in a clinical questionnaire inside SurveyNinja.

2. Fatigue assessment

For chronic illness, cancer treatment, post-viral fatigue, or intense training plans, fatigue is one of the key variables.

VAS can capture self-reported fatigue from "not tired at all" to "maximum possible fatigue", and then:

• correlate with lab or performance metrics,
• monitor response to treatment or rehab,
• adjust workload in sports or physiotherapy.

3. Emotional states (anxiety, mood, depression)

VAS can be adapted to evaluate:

• anxiety ("not anxious at all" → "extremely anxious"),
• mood ("worst possible mood" → "best possible mood"),
• tension, stress, or perceived burden.

It is often used alongside standardized scales, or as a quick screening / daily tracking tool inside mental health or wellbeing surveys.

4. Quality of life and overall well-being

In quality-of-life studies, a global VAS can summarize how the person evaluates:

• their life in general,
• health-related quality of life,
• satisfaction with treatment or living conditions.

Here, VAS becomes a compact "headline" indicator that complements detailed multi-item questionnaires.

5. Hunger and satiety in nutrition research

In dietetics and nutrition studies, VAS is used to measure:

• hunger,
• satiety,
• desire to eat specific foods.

Participants mark points like "not hungry at all" → "as hungry as I can imagine." This helps evaluate meal plans, dietary interventions, and appetite regulation.

6. Dyspnea (shortness of breath)

In pulmonology and cardiology, VAS can quantify:

• breathlessness at rest,
• breathlessness during exertion,
• changes over the course of treatment.

Patients rate their shortness of breath from "no shortness of breath" to "worst possible shortness of breath."

7. Physiotherapy and sports medicine

During rehabilitation or training, VAS can track:

• discomfort during exercises,
• pain after load,
• perceived exertion.

In many projects, VAS is collected via cross-sectional surveys at a single time point, or via panel and longitudinal studies to observe changes and avoid panel attrition.

How to Use VAS Effectively

To get reliable, comparable data from VAS, it's important to follow a structured approach.

1. Give clear instructions

Make sure respondents fully understand:

• what the two ends of the scale represent,
• what kind of sensation they should rate (pain right now, overall mood today, etc.),
• where to put their mark.

In digital surveys, add short helper text or tooltips. A clear instruction like in a good survey question example significantly increases data quality.

2. Keep the scale format consistent

Use the same line length (commonly 10 cm) and the same anchor wording:

• across all participants,
• across all measurement points,
• across all related studies, if you want to compare them.

Consistency is critical for valid comparison over time.

3. Train the staff (or research team)

Anyone who presents the scale to participants should:

• know how to explain it simply,
• avoid suggesting "good" or "bad" answers,
• understand how to read and record VAS scores accurately (e.g., in millimeters).

In online form builders like SurveyNinja, the system can automatically convert slider positions to numerical values, which simplifies training and reduces manual errors.

4. Consider your target group

Think about:

• age (children may need simplified visuals),
• cultural context,
• language skills,
• cognitive or physical limitations.

Adapt the design if necessary - for example, with bigger fonts, clearer labels, or additional examples. For remote data collection, you can combine VAS with other accessibility-friendly question types.

5. Plan your analysis ahead

Before collecting data, decide:

• how exactly you will convert marks into scores (e.g., mm from the left end),
• which summary metrics you need (means, medians, distributions),
• what statistical tests or comparisons you'll run.

If you know this upfront, it's easier to structure the questionnaire and data export in your survey tool. In SurveyNinja, you can set up data exports and integrations to push VAS data into your statistical software or BI tools.

6. Create a comfortable environment

Respondents should feel:

• safe to express their real sensations,
• not judged for "high" or "low" scores,
• not rushed unnecessarily (even though VAS is quick).

This is especially important in clinical and mental health contexts.

7. Use repeated measurements when needed

If you want to track change over time, schedule repeated VAS measurements:

• before and after treatment,
• daily/weekly tracking,
• before/after specific events (physio session, workout, therapy session, etc.).

Automation via recurring and triggered surveys helps collect this data without manual reminders.

8. Be careful with multiple VAS at once

It's possible to use several VAS scales in a single survey (for pain, fatigue, anxiety, etc.), but:

• don't overload respondents,
• clearly label each scale,
• group related items logically.

If the form becomes too long or confusing, split it into several short surveys or use survey logic and branching to show only relevant scales.

Conclusion

The Visual Analogue Scale is a simple idea with a lot of power behind it: a straight line that turns subjective feelings into precise numbers.

Used correctly, VAS helps:

• capture subtle changes in pain, fatigue, or mood,
• enrich clinical and UX research,
• improve the quality of treatment, training, and product decisions.

If you want to experiment with VAS in your own projects, you can set it up as a slider question in SurveyNinja using one of the research survey templates, then track and analyze the scores alongside other metrics like NPS, CSAT, and CES.