Thursday, February 5, 2026
think different
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indictment
Monday, February 2, 2026
thumb it
# The Most Practical Software Estimation Rules of Thumb
*Extracted from Hacker News discussion on "How I Estimate Work as a Staff Software Engineer" (143 comments)*
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## 1. The "Multiply by Pi" Rule *(Most frequently cited)*
Multiply your initial estimate by **π (3.14)**. This comes from Alistair Cockburn and was mentioned by multiple commenters as having an "almost magical" corrective effect.
> *"The old guys in the 80's and 90's would say kiddingly multiply your original estimate by pi"* — shoknawe
**Variant:** One commenter's mentor said: *"Make the estimate in great detail. Then multiply by 2. Then double that number."* (Effectively 4x)
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## 2. The "Bump the Unit" Rule
Take your estimate and move to the next human time unit:
- A few days → **a week**
- A week → **a month**
- A month → **a year**
- A year → **a decade or never**
> *"It's wildly pessimistic but not as inaccurate as I'd like."* — dcminter
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## 3. The "Orders of Magnitude" Method *(Highly practical)*
Don't estimate precise numbers. Instead, answer these questions:
- Is it going to take more than **2 hours**?
- More than **2 days**?
- More than **2 weeks**?
- More than **2 months**?
- More than **2 years**?
If the estimate is too wide, break it into smaller chunks. If you can't break it down, decide if it's worth gathering more information—or scrap the project.
> *"If you can answer these questions, you can estimate using a confidence interval."* — xn
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## 4. The "Two Days or Less" Threshold
Gather the team. For each task, on the count of three, everyone gives thumbs up (can ship in ≤2 days) or thumbs down.
If it's thumbs down, **break it down further** until you have thumbs-up tasks.
> *"It generally implied if we collectively thought a task would take more than two days to ship, it may require breaking down."* — hosainnet
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## 5. Invert the Process: Start with the Deadline
Don't ask "how long will this take?" — **find out the time budget first**, then work backwards to determine what scope is achievable.
> *"Someone already has a time constraint. There's already a deadline. Always. Find out what it is and work backwards."* — fogzen
> *"Instead of asking for an estimate, why don't they say: we have until date X, what can we do?"* — etamponi
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## 6. Estimate in Work Hours, Then Track
The only meaningful unit is **actual work hours**. And critically: **follow up on every estimate** to improve calibration.
> *"My team had several months when we were within ±10% in the aggregate"* — tuna74
> *"If you don't close the loop, if you don't keep track of what you estimated vs. how long it took, how are your estimates going to get better? They aren't."* — AnimalMuppet
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## 7. The 2x Rule (for Experienced Teams)
Simply **double your initial coding estimate** to account for non-coding work (planning, testing, integration, communication).
> *"As a rule of thumb, 1.5x or 2x your raw coding time estimate"* — cited from Vadim Kravcenko
**For inexperienced teams:** Use **3x**.
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## 8. Ballpark First, Details Later
Counterintuitively, rough ballpark estimates are often **more accurate** than detailed work breakdowns, because breakdowns miss unknowns.
> *"I find that ballpark estimates are often more accurate than estimates based on work breakdowns"* — fallinditch
One commenter described abandoning a year's worth of detailed Gantt charts, getting a developer's gut estimate of "2 months," adjusting to 14 weeks—and it took exactly 14 weeks.
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## 9. The Tracer Bullet Approach
Before estimating a large project, build a quick **end-to-end proof of concept** that touches all the tricky parts. This surfaces unknowns early and makes subsequent estimates much more tractable.
> *"Making estimates then becomes quite a bit more tractable"* — cube2222
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## 10. Present Options, Not Points
Never give a single number. Return with **multiple plans at different risk levels**:
- **Plan A:** Aggressive timeline if X, Y, Z all go right
- **Plan B:** Safer approach with tradeoffs
- **Plan C:** Requires external help
> *"I never come back with a flat 'two weeks' figure. I come back with a range of possibilities, each with their own risks."* — original article
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## The Meta-Rule (Most Important)
### Scope is flexible. Dates are not.
The real skill isn't predicting how long things take—it's negotiating scope to fit the available time. Features can always be cut, simplified, or phased.
> *"Scope is always flexible. The feature or commitment is just a name and a date in people's heads. Nobody but engineers actually care about requirements. Adjust scope to fit the date, everyone is happy."* — fogzen
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## Quick Reference Summary
| Rule | Multiplier/Method |
|------|-------------------|
| Pi Rule | Initial estimate × 3.14 |
| Double-Double | Detailed estimate × 2 × 2 |
| Bump the Unit | Days → Weeks → Months → Years |
| 2x Rule | Coding time × 2 (or 3x for new teams) |
| Orders of Magnitude | >2hrs? >2days? >2wks? >2mos? |
| Two Days Threshold | If >2 days, break it down |
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## Key Insights from the Discussion
### Why Estimation is Hard
1. **Unknown unknowns dominate** — The work you can't predict always takes 90% of the time
2. **Estimates are political tools** — They're used by management to negotiate resources, not to plan engineering work
3. **Precision ≠ Accuracy** — Detailed breakdowns often miss more than gut estimates
### What Actually Works
1. **Track your estimates** — Close the feedback loop to improve over time
2. **Start with constraints** — Find out the real deadline before estimating
3. **Pad scope, not time** — Having features you can cut gives you execution-time flexibility
4. **Communicate early** — Surface problems as soon as you see them, not at the deadline
### The Uncomfortable Truth
> *"It is not possible to accurately estimate software work. Software projects spend most of their time grappling with unknown problems, which by definition can't be estimated in advance."* — Sean Goedecke (original article)
But this doesn't mean you shouldn't estimate—it means you should estimate **differently**: focus on unknowns, present ranges, and negotiate scope rather than pretending you can predict the future.
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*Source: https://news.ycombinator.com/item?id=46742389*