Screen time and digital eye strain calculators both turn your device habits into a single scored estimate, but they look at different parts of the same day. Screen time measures how much you use each kind of screen and how much of that happens close to bedtime. Digital eye strain measures how comfortable your setup is — distance, lighting, breaks, and eye conditions — for whatever hours you already spend. One quantifies the habit; the other explains why the same habit can feel harder on some days.
What each calculator does
The screen time calculator takes an age group, a primary use, and three device categories — computer or laptop, smartphone or tablet, and TV or gaming — plus the portion of that total falling within two hours of bedtime. Total screen time is the direct sum of the device hours (capped at 24), and the impact score weights computer hours at 1.0, smartphone at 1.2, TV or gaming at 0.8, and nighttime hours at an extra 1.5. A low risk label applies at or below 50 points and moderate above. It also suggests a break schedule — every 2 hours for computer, every 30 minutes for phone, every hour for TV or gaming — and adds the 20-20-20 rule when the total exceeds 4 hours, with age-group prompts (for example, adults over 8 hours are prompted toward 6 to 8).
The digital eye strain calculator takes daily screen hours, break frequency and duration, screen distance, lighting, and an existing eye condition. Each hour contributes 4 points; distance applies 1.5 (too close), 1.0 (arms length), or 1.2 (too far); lighting applies 1.4 (too dark), 1.0 (moderate), or 1.3 (too bright); conditions add a small multiplier such as 1.3 for dry eyes. The break benefit — (60 ÷ break frequency) × break duration × 0.1 — divides the base, and the score is capped between 0 and 100 with labels from Low to Very High. Its default example (8 hours, a 5-minute break every 30 minutes, neutral setup) scores 16/100, and the page shows how changing to a too-close, too-dark setup raises the same hours to 34/100.
Side-by-side
| Screen time calculator | Digital eye strain calculator | |
|---|---|---|
| Inputs | Age group, primary use, device hours (computer, phone, TV/gaming), nighttime hours | Screen hours, break frequency, break duration, distance, lighting, eye condition |
| Primary output | Total daily hours plus a weighted impact score | A 0–100 habit-based strain score |
| What the weights capture | Quantity and timing: device categories and 1.5x nighttime use | Environment: distance, lighting, and condition factors around the same hours |
| Break guidance | Per-device cadence plus the 20-20-20 rule over 4 hours | 5-minute breaks every 20/30/60 minutes depending on the score band |
| Risk labels | Low at or below 50 points, moderate above | Low, Moderate, High, and Very High bands across 0–100 |
| Typical question | How much time am I spending on screens, and when? | Why do my eyes feel strained during my screen time? |
| Output precision | Hours and score to one decimal | Whole-number score out of 100 |
When to use which
Use the screen time calculator when you want the audit: the shape of a day by device, how much of it is late-night use, and how the total compares with age-based planning prompts. Its device split makes the next step concrete — if smartphone time dominates, the recommendations target phone habits; if computer time is unavoidable, they protect the evening instead.
Use the digital eye strain calculator when the hours are settled but the comfort is not. Because it separates time from setup, it shows whether a dark room, a screen that is too close, or skipped breaks are raising the strain of a schedule that looks fine on paper. The two pages are designed to be used together — each one links to the other — and both are habit-estimation tools whose scores are meant for comparison, not diagnosis.
Limits and disclaimer
Both pages are educational only and are not medical assessments. The screen time impact score is a page-defined heuristic, and the eye strain score is a deliberately simple weighted model whose factors are not a medical risk model. The screen time page warns against double-counting hours across device fields and against reading its score as a diagnosis of eye strain, sleep trouble, or attention issues; the eye strain page warns that tired eyes, dryness, blur, and headaches have many causes and that persistent or severe symptoms warrant an eye care professional. Neither calculator sets a universal “safe” amount of screen time, and both present their thresholds as planning prompts rather than official limits.