Scroll Depth Calculator
The formula
What the scroll depth tells you
Models how far readers travel and what share survive to see any element at a given depth — the placement physics below the fold.
Calculation: Exponential depth decay: reach ≈ sessions × e^(−CTA depth ÷ avg depth) with depth as mean. Enter your inputs and every substitution is shown below the result.
Reading the result
Anything past the two-thirds depth mark is decoration for most commercial pages; CTA placement is decided by the decay curve, not by taste.
Rules of thumb: Average depth 40–60% on article pages, 15–30% on broad landing pages
Limitations and best practice
The exponential model fits long-form articles best; short pages plateau and quizzes spike — check real depth histograms before moving furniture.
This calculator gives an estimate based on standard formulas; it is not professional financial, medical, legal or engineering advice. Verify anything you plan to act on with a qualified professional and your own records.
Frequently asked questions
Do sticky bars beat in-flow CTAs?
What counts as good scroll depth?
Source & methodology
Scroll-analytics convention.
Scroll Depth: what this tool answers
This page was written for one job: turning your own inputs into a defensible figure, with the working shown. Scroll Depth is the kind of number people argue about from memory. This page ends that argument with arithmetic you can watch happen: enter your figures, get Sessions reaching the CTA in real time, and see every substitution printed below.
A calculation like this one is worth roughly as much as a careful sentence: it forces several vague considerations into one comparable quantity. Once Scroll Depth is on the table, the argument can stop being about impressions.
In plain terms, Scroll Depth answers the question "Sessions reaching the CTA?". The measurement matters because it converts a situation that feels complicated — several inputs pulling in different directions — into a single number you can act on. Within Business & Entrepreneurship, Marketing & Growth is the context where this figure is quoted most often, and professionals treat it as a first-pass screen rather than a verdict.
Nothing below is stock text pasted around a number: the worked example computes sessions reaching the CTA = 4,786.6 from this tool’s own defaults, and the sensitivity section ranks the inputs that move the result — CTA sits at page depth first, at ≈21.2 % of the headline for a ten-percent error either way in that input. Work down the page and by the end you could re-derive the result in a spreadsheet from memory.
Inside the Scroll Depth calculation: formula and every input
Here is the complete model this tool runs — Exponential depth decay: reach ≈ sessions × e^(−CTA depth ÷ avg depth) with depth as mean — with each input explained below. If a competitor’s page gives you a different answer from the same inputs, this is the text that settles which of you is right.
Sessions on the page (example value 32,750) is a measured number in the unit named by the label; the formula does not convert for you. This input feeds the formula directly; a defensible figure here is worth more than false precision anywhere else.
Average scroll depth (%) (example value 52) is a numeric input whose unit is fixed by the label; a wrong unit is a wrong answer wearing a plausible disguise. Check the convention first: if the source says “6.5 % per year”, type 6.5 and let the formula do the rest.
CTA sits at page depth (%) (example value 100) is a plain measured quantity — the unit shown in the label is the unit the formula expects. Enter it exactly as your document states it — quoted annual, monthly and effective rates are three different numbers.
A fully worked Scroll Depth example
Rather than describe the calculation, here it is end to end — every substitution in order, starting from the inputs above. Starting figures: Sessions on the page, Average scroll depth (%), CTA sits at page depth (%). The endpoint of that chain is 4,786.6 of sessions reaching the CTA, sitting in the “15% of sessions see it — move it above the 36% half-depth to keep visibility” band.
- Model mean depth = 52%; decay e^(−100/52) = 0.146
- Reach = 32750 × 0.146 ≈ 4787 sessions
Share of sessions reaching — 14.6 %. Read next to the headline, this is the figure that shows the shape of the trade-off.
Depth where half the readers are gone — 36.0 %. Read next to the headline, this is the figure that shows the shape of the trade-off.
Extra CTAs viewed at depth 36% — 11,588.4. If your inputs change, this is usually the first companion figure to move.
Keep this worked example open while you enter your own figures: matching the shape of the substitution is the fastest way to spot a unit or convention mistake.
Scenario table: Scroll Depth at ±10 % and ±20 % of the key input
The honest version of any estimate is a corridor, and this one is cheap to produce: Scroll Depth was recomputed at 5 points along the dominant input, with every other field left untouched.
| CTA sits at page depth setting | Sessions reaching the CTA |
|---|---|
| 80 % of the example value | 7,031.8 |
| 90 % of the example value | 5,801.6 |
| example inputs | 4,786.6 |
| 110 % of the example value | 3,949.2 |
| 120 % of the example value | 3,258.3 |
That spread — 3,258.3 at the low end, 7,031.8 at the high — is what a careful read of Scroll Depth looks like: a band you can state out loud, with the reason for each edge. Reproduce it in the form above by editing CTA sits at page depth alone; the substitution steps will follow your figures exactly.
The levers behind Scroll Depth, ranked by effect
Nobody should have to guess which input matters. The engine was re-run once per field below — ten percent up, ten percent down, everything else frozen — and the results ranked by how far they moved the sessions reaching the CTA. For Scroll Depth the ranking is measured rather than guessed, and it belongs to these defaults: shift the starting point and the order can shift with it.
- Nudge CTA sits at page depth by ±10 % and Scroll Depth lands between 3,949.2 and 5,801.6 (sensitivity ≈21.2 %)
- Average scroll depth: ten percent up gives 5,701.1, ten percent down gives 3,865.7 — ≈19.2 % of the sessions reaching the CTA either way
- Sessions on the page +10 % → Scroll Depth = 5,265.3 · −10 % → 4,308.0 (the sessions reaching the CTA shifts ≈10.0 %)
CTA sits at page depth is the dominant lever here: ten percent either way moves the result by about 21.2 %, from 3,949.2 to 5,801.6. Spend your verification effort there first, and treat Average scroll depth as the second priority (≈19.2 % per ten percent). The remaining fields can sit at safe defaults without materially changing the answer — knowing which is which is what separates a careful calculation from an anxious one.
What a Scroll Depth of 4,786.6 means in practice
Nobody acts on a bare figure — they act on a figure with a comparison attached. On the example inputs the band reads “15% of sessions see it — move it above the 36% half-depth to keep visibility”; your own figures place you on a different rung of the same ladder. The sensitivity list shows how far a modest input error moves you along that ladder: for CTA sits at page depth, ±10 % covers 3,949.2 to 5,801.6. The practical reading rules: read the band as a starting hypothesis, then test it: change the two dominant inputs by ten percent and see whether the verdict survives. Verdicts that survive stress are the ones worth acting on.
The comparison worth making is not with somebody else’s Scroll Depth but with the version of your own situation measured last quarter — same formula, same conventions, different inputs.
Common mistakes with Scroll Depth (and the fix)
The exponential model fits long-form articles best; short pages plateau and quizzes spike — check real depth histograms before moving furniture. This calculator gives an estimate based on standard formulas; it is not professional financial, medical, legal or engineering advice. Verify anything you plan to act on with a qualified professional and your own records.
Reading Scroll Depth as a promise rather than a conditional. Every number here is of the form “if these inputs, then this result”; when an input moves, the honest response is to recompute rather than to defend the old figure.
One mistake is specific to this engine: assuming every input matters equally. The computation above shows CTA sits at page depth dominating — a careful figure there beats false precision everywhere else.
Another is comparing across contexts: a Scroll Depth computed with one set of conventions should never be lined up against a figure computed with another. Check the inputs behind both before ranking them.
Six things to confirm before acting on Scroll Depth
- Note the date and the inputs beside the number so the figure can be audited later.
- Verify each input against its original source document, not memory.
- Check CTA sits at page depth before anything else: it is the measured dominant input, ≈21.2 % of Scroll Depth per ten percent.
- Re-run the calculation with a ±10 % stress on the two most sensitive inputs.
- Compare the output against one published benchmark or a colleague’s independent estimate.
- Run the ±10 % stress on the top two levers and check that your conclusion survives both.
How to use the Scroll Depth tool properly
Using a calculator well sounds trivial, but the difference between a decision-grade figure and a throwaway one lives entirely in the routine. The routine for Scroll Depth takes a minute to learn and applies to every input above.
Step 1 — start from evidence. The inputs behind Scroll Depth are sessions on the page, average scroll depth (%), cta sits at page depth (%). Write them down with their source next to each one; if you cannot name where a figure came from, that is the input most likely to be wrong. Re-running a number costs seconds; retracting a decision costs considerably more.
Step 2 — enter the conservative case first. Resist the flattering scenario. Type the inputs you would defend in front of a sceptical reader, read the Sessions reaching the CTA (4,786.6 for the example values), and note the verdict band. Numbers are cheap to produce and expensive to retract; the extra minute is the cheapest insurance available.
Step 3 — isolate your variables. Change one field, observe, revert. The live sensitivity list does the ranking for the default inputs; verify it against your own, because dominance shifts when the starting point shifts. Write the assumptions in the same file as the result, and future arguments take minutes instead of meetings.
Step 4 — ask what would have to be true. Take the result you want and work backwards through the inputs until you find the assumption that produces it; then decide honestly whether that assumption is defensible. Suspiciously tidy answers deserve the same scrutiny as untidy ones.
Step 5 — record the context, not just the number. Note today’s date and the inputs alongside the 4,786.6 output. Six months from now the context is what turns this figure into a trend. A result worth acting on survives having its two shakiest inputs halved.
Who actually uses Scroll Depth — and when
Most Marketing & Growth disagreements are arithmetic disagreements in disguise. When Sessions reaching the CTA of 4,786.6 sits on the table with its working shown, the conversation stops being about who sounds more confident and starts being about which input is wrong. Note the assumption you are least sure about; that is where the real risk lives.
Used properly this is a five-minute filter that saves weeks. Compute Scroll Depth, reject what fails, and only then bring in the expensive analysis for the survivors. A figure with a date beside it becomes evidence; without one it stays an anecdote.
There is a personal-administration use people overlook: periodic self-checking. Scroll Depth quietly drifts as life changes — rates move, bodies change, costs compound — and re-running it a few times a year catches drift while correction is still cheap. One decimal place more than your data supports is one decimal place of fiction.
Scroll Depth — frequently asked questions
What affects Scroll Depth the most?
Measured on this engine, CTA sits at page depth is the dominant lever: moving it ±10 % shifts the sessions reaching the CTA across 3,949.2 to 5,801.6 — about 21.2 % of the headline, with Average scroll depth next at ≈19.2 %. The ranked list in the sensitivity section is computed live, not asserted from a template.
Which matters more: average scroll depth or cta sits at page depth?
By the numbers, CTA sits at page depth: a ten-percent change in it moves the result ≈21.2 %, versus ≈19.2 % for Average scroll depth. Spend your measuring effort in that order — precision on the weaker lever buys almost nothing.
What is a typical Scroll Depth?
On the worked example above Scroll Depth comes out at 4,786.6. Treat that as one point on a distribution rather than a norm: the bands, the companion outputs and the sensitivity ranking tell you how wide the plausible range really is.
How do I calculate Scroll Depth by hand?
Use the stated model — Exponential depth decay: reach ≈ sessions × e^(−CTA depth ÷ avg depth) with depth as mean — and substitute in the order the tool prints (it starts from Model mean depth = 52%; decay e^(−100/52) = 0.146). On the example inputs the hand route lands on 4,786.6, exactly what the calculator shows. A spreadsheet reproduces it in two or three cells; doing it once by hand is what makes the automated answer trustworthy.
What happens to Scroll Depth if cta sits at page depth changes by 10 %?
Try it in the form above and the printed substitution will follow you; the pre-computed answer for the defaults is 3,949.2 to 5,801.6 across the ten-percent probe, i.e. ≈21.2 % sensitivity on the sessions reaching the CTA.
Is the Scroll Depth result of 4,786.6 good or bad?
Neither, on its own — the label “15% of sessions see it — move it above the 36% half-depth to keep visibility” is the band this figure falls in for the example inputs, and your own inputs will place you elsewhere on the same ladder. Judge the number against your history and your alternatives, and remember that a ten-percent error in CTA sits at page depth alone moves it by ≈21.2 %.
How do I calculate Scroll Depth manually?
Write down the inputs, then follow the printed steps in order — Exponential depth decay: reach ≈ sessions × e^(−CTA depth ÷ avg depth) with depth as mean. A spreadsheet replicates it with two or three cells. The manual route is worth doing once to build intuition; after that the calculator saves time and eliminates transcription slips.
What affects Scroll Depth the most?
Sensitivity depends on where you start, but the inputs Sessions on the page and Average scroll depth (%) typically move Scroll Depth further than the rest because they enter the formula multiplicatively. If you can only measure two things well, measure those and hold the others at conservative defaults.
Do sticky bars beat in-flow CTAs?
For long pages, yes — persistent 20–30% lift on secondary CTAs; cap the sticky at one element or it competes with itself.
What counts as good scroll depth?
The CTA-reach share is the metric that pays — depth itself is just the mechanism; report reach and conversion by placement.
Can this tool see the numbers I type?
It cannot. There is no submission step: the calculation happens in your browser and the result disappears when you close the page. Treat the fields above as a scratchpad rather than a form.
Key terms on this page
- Share of sessions reaching
- 14.6 % in the default Scroll Depth calculation — one of the secondary figures an experienced reader checks before trusting the primary number.
- Depth where half the readers are gone
- 36.0 % in the default Scroll Depth calculation — one of the secondary figures an experienced reader checks before trusting the primary number.
- Extra CTAs viewed at depth 36%
- 11,588.4 in the default Scroll Depth calculation — one of the secondary figures an experienced reader checks before trusting the primary number.
- Sessions reaching the CTA
- The primary output of this tool: 4,786.6 for the default inputs, computed exactly from Exponential depth decay: reach ≈ sessions × e^(−CTA depth ÷ avg depth) with depth as mean.
- Worked example
- The calculation written out in full so that nothing on this page has to be taken on trust.
- Verdict band
- The plain-language label — here “15% of sessions see it — move it above the 36% half-depth to keep visibility” — mapping the computed figure onto experience-based ranges for Business & Entrepreneurship.
- Sensitivity (±10 %)
- How far the Scroll Depth moves when a single input is nudged ten percent either way; the ranked list on this page is computed live from this engine.
Where the Scroll Depth model comes from
Everything above runs on one stated formula, applied without hidden coefficients: Exponential depth decay: reach ≈ sessions × e^(−CTA depth ÷ avg depth) with depth as mean. Source of record: Scroll-analytics convention. Specialist software layers extra coefficients on top of the same algebra; none are hidden here, and that transparency is what makes a disagreement traceable to a specific input instead of a black box.
Nothing here replaces a qualified professional, and nothing here is approximate either — the arithmetic is exact, and the honesty is in the inputs you supply. Nothing is smoothed, weighted or adjusted behind the scenes; where judgement enters, this page says so and names the input responsible.
Turning this Scroll Depth into a decision
Save the number together with its inputs and today’s date; a Scroll Depth figure without context is unusable the moment an input changes.
The audience here is people who need one trustworthy number before their next decision. Everything you need to defend the result — formula, substitution, sensitivity, source — is printed above, so the only remaining variable is the honesty of your inputs.