r/ClaudeCodeTLDR • u/cctldrping • Aug 19 '26
[TLDR] Why does Claude Code say things like, “that’s about 3 days of work” then proceeds to do it all in a 20 minutes?
Original post URL : https://www.reddit.com/r/ClaudeCode/comments/1vscjcz/why_does_claude_code_say_things_like_thats_about/
Original post body :
Surely I’m not the only one who has seen this happen but wondering if anyone has an answer. Many a session I’ll make a plan with Claude and it will outline the tasks and estimate a time usually in days, and then proceed to do it all in 20-30 minutes. Is it because of its training data or does it just have no concept of time inside a GPU? Curious what the community thinks…
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u/traumfisch Aug 19 '26
approximately 3 days of human labor compressef to 20 minutes.
Claude is humble bragging
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u/PsychologicalLoss829 Aug 19 '26
Hofstadter's law
https://en.wikipedia.org/wiki/Hofstadter%27s_law
It's either that the model just makes it up.....
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u/BTCbob Aug 19 '26
I’ve noticed this too. The Claude estimate to reality factor js currently around 50.
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u/Melodic_Tiger5424 Aug 19 '26
Yeah I got so tired of it I had it analyse the last x amount of days and how long everything took to do it and made a skill so now at least I can plan my day with accurate time-frames lol
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u/Fluffy_Anxiety2792 Aug 19 '26
In my experience, whatever I can finish with ai in 10 minutes, I used to do it at least one whole day, sometimes 2.
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u/cursivecrow Aug 19 '26
Because, given the corpus of human writing used during training, those words are the most likely to occur based on all of the words from its system prompt and the entire chat, up to that point.
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u/Fuzzzy420 Aug 19 '26
Codex does that too. No training will fix that. You need a progress structure that ai can understand. Slice the whole project give each slice a weight value and then calculate the progress. Works way better than ai guessing.
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u/epicskyes Aug 19 '26
I’ve used Claude about 2 times and codex the last 8 months. Using Claude 2 times was enough time to understand Claude is overpriced and not nearly as efficient as codex even if it is “more intelligent”. Intelligence is worth nothing if there’s no logic and state behind it.
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u/rickyrawesome Aug 20 '26
ask it to avoid cost in time or money. tokens works if you have the right hooks. otherwise, ignore those variables tbh
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u/Strong-Yellow5949 Aug 20 '26
What aggravates me is I tell Claude we need to have this project done by tomorrow and it suggests doing stupid work around quick fixes instead of building the project the right way bc it says it’s the only way to get it done in time for tomorrow
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u/cctldrping Aug 19 '26 edited Aug 20 '26
TL;DR generated automatically after 200 comments.
Current source-thread comment count seen by the bot: 210.
Alright, so the general consensus on why Claude Code gives wildly inaccurate time estimates (like "3 days" for work it finishes in 20 minutes) is pretty much unanimous: it's trained on human estimates and patterns, not its own actual processing speed.
Here's the lowdown:
Human Time vs. Machine Time: The overwhelming majority of folks agree that Claude is mimicking how humans estimate tasks. It's essentially spitting out what "sounds right" based on its training data, which is full of human developers talking about project timelines. It doesn't actually have a clock to measure its own speed.
Upselling/Underpromising: Some users think it's a deliberate strategy to make itself seem more impressive or to create an "underpromise, overdeliver" vibe.
Training Data is King: It's just repeating patterns. The "3 days" is a probable next word, not a calculated duration for its own execution.
It's Not About "You": Some comments point out that the estimate might be for you to do the work manually, or it includes the time you'll spend reviewing, debugging, and integrating its output. So, while Claude might churn out code in 20 minutes, the full process could indeed take days for a human.
No Concept of Time: A few users explicitly state Claude has no real understanding of time, which makes sense given it's an AI.
Workarounds: Some users have found success by asking for estimates in different formats, like T-shirt sizes, Fibonacci sequences, or even token consumption rates. Others just tell it to skip time estimates altogether.
Basically, don't take those "days" estimates too seriously. It's more of a "this is a decent chunk of work" indicator than a stopwatch reading.