Guide
Why your playlist length calculator stops at 100 videos
Updated 2026-10-01 · 5 min read
In September a JEE student on Reddit, choosing between Class 11 physics courses, listed the lengths of three popular YouTube playlists: 83.5, 91.4 and 87 hours. Three courses of about the same size, so the choice comes down to the teacher.
Except they are not the same size. Counted to the end, the three come to 98, 455 and 184 hours, and one of them is nearly five times as long as another. The tool the student used had added up the first 100 videos of each playlist and stopped there, without saying so.
This guide is about why so many tools stop at 100, how to tell when a total has been cut short, and what the difference does to a study plan.
The three courses, counted twice
| Course | Videos | Tool said | First 100 | All |
|---|---|---|---|---|
| Physics Wallah | 117 | 83.5 h | 83.5 h | 98 h |
| Unacademy | 440 | 91.4 h | 91.2 h | 455 h |
| ABJ Sir | 178 | 87 h | 87.1 h | 184 h |
Measured on 1 October 2026: Physics Wallah's Class 11 physics for JEE Main and NEET, Unacademy JEE's complete Class 11 physics from JEE Live Daily, and Athera's Class 11 physics by ABJ Sir. The student's figures match the first 100 videos of each playlist to within a quarter of an hour. Eleven of the Unacademy playlist's 440 videos are private or deleted, so 429 of them count. See all three side by side →
What it does to a plan
At two hours a day, the student's numbers say each course takes about six weeks. The real ones say:
- Physics Wallah: 49 days, seven weeks.
- ABJ Sir: 92 days, three months.
- Unacademy: 228 days, seven and a half months. Even watched at 2×, it needs 114 days at two hours a day.
That is one subject of three. Which course is best is a separate question, but it cannot be answered from the cut-off numbers. A student who picked the "91-hour" course to finish by the end of term would find out in week six that they were a fifth of the way through.
The giveaway: everything comes out near 90 hours
Three different courses landing within eight hours of each other is the sign. That is what 100 lectures of 50-odd minutes add up to: the first 100 videos of these three playlists average 50, 55 and 52 minutes. When a tool gives every long course roughly the same total, it is counting the same number of videos in each.
Why so many tools stop at 100
YouTube's playlist page sends 100 videos at a time
Open that Unacademy playlist on youtube.com and the header says 440 videos, but the page arrives with the first 100. The next batch loads only when you scroll to the bottom. Anything that works by reading the page — a bookmarklet, a snippet pasted into the browser console, an extension that adds up what is on screen, a website that downloads the page behind the scenes — sees those 100, unless it asks YouTube for the next batch or someone scrolls to the very end first.
YouTube's API sends 50 at a time
Tools built on the YouTube Data API ask for a playlist 50 videos at a time, then make a second call for those 50 videos' lengths. Every call spends part of a daily quota (10,000 units by default) that the tool shares among all its visitors. Following a playlist to its end means asking again until YouTube says there is nothing left. A tool that stops after two pages, to save quota or to answer faster, stops at exactly 100.
Either way, the total looks finished
Neither cut-off produces an error. You get a confident number with no "at least" in front of it. Other tools stop at 500 instead. The number differs; the problem is the same.
How to tell if a total was cut short
- Compare the video count with YouTube's. YouTube shows the count under the playlist's title. If the tool counted exactly 100, or 500, or any other suspiciously round number, and YouTube says more, it stopped early. A gap of a few videos is normal: those are private or deleted (more on that).
- Look at the end of the list. If the tool shows the videos it counted, the last one should be the playlist's last video.
- Be suspicious of totals that agree. Long courses vary enormously. If every one you check comes out between 80 and 95 hours, the tool is counting 100 lectures, not courses.
How this site counts
Paste a playlist into the calculator and it is counted to the end, up to YouTube's limit of 5,000 videos per playlist. The count beside the total is the playlist's own, minus private and deleted videos, which are listed as unavailable rather than silently dropped.
We have a ceiling of our own, and it shows. One lookup reaches about 850 videos, so a longer playlist is counted in stretches: the label beside the count reads counting 850 of 3,140… while the total grows, and the page fills in the full list when it gets to the end. If counting stops short, the page says so (first 850 of 3,140) and the total covers exactly the videos listed. A channel's uploads are counted newest first, and the channel page says how far back it got.
That is the rule a cut-off total breaks: a number here is either the whole playlist, or it says which part it is.
Before you choose a course by its length
Length is a fair way to choose. With an exam date, it may be the most important number there is. Paste each candidate in, check the count against YouTube's, and plan against the whole total. Then finishing a YouTube course before your exam turns that total into hours a day, and the best free course lists give live totals for popular courses.
Frequently asked
Does YouTube show a playlist's total length anywhere? Not on the playlist page. It shows the number of videos and each video's length, but not the sum. The ways to get it are in how to see the total length of a YouTube playlist.
My count is a few lower than YouTube's. Is that the same problem? Usually not. YouTube's count includes private and deleted videos, which nobody can watch or measure. We list them as unavailable; see why the playlist duration looks wrong.
Can speed rescue a 455-hour course? Partly. At 1.5× it is 303 hours, and at 2× it is 228: still months. Watch time at 1.25×, 1.5× and 2× covers what speed costs you in understanding.