> ## Documentation Index
> Fetch the complete documentation index at: https://help.partgenie.ai/llms.txt
> Use this file to discover all available pages before exploring further.
# Engineering calculator
> Built-in power and thermal checks in Search, with Intelligent UI sliders for local what-if tuning
Search can run **engineering calculations** inside the answer—not a separate calculator app. PartGenie picks the audit that fits your question, shows the formulas, runs **Pass / Fail** checks when limits apply, and attaches an **Intelligent UI** panel you can tune without a new search.
## Which calculators appear today
PartGenie maps your question to an audit panel. The set grows over time; these are the main ones shipping now:
| Audit panel | What it calculates | Typical checks | Key inputs |
| - | - | - | - |
| **Resistor power rating** | Dissipation **P = V²/R**, **P = VI**, or **P = I²R** and **margin** vs rated wattage | Electrical — is rated power enough? | Voltage, resistance (or current), resistor rating (W) |
| **LDO power dissipation & junction temperature** | Drop power **Pd ≈ (Vin − Vout) × Iout** (plus quiescent current when relevant), **Tj = Ta + Pd × θJA** vs Tj(max) | **Electrical** · Pass/Fail, **Thermal** · Pass/Fail | Vin, Vout, Iout, Ta, θJA, junction limit |
When a limit is missing, PartGenie may **assume reasonable defaults** (for example ambient 25°C or a typical θJA) and say so in the answer—or **stress-test above your stated load** (e.g. 400mA when you asked 200mA) so you see headroom, not only nominal.
Name the part or paste **θJA** / **Tj(max)** from the datasheet when you have them. PartGenie can ground limits in manufacturer data; generic audits still work with numbers you provide in the question.
## How to ask (example queries)
Stay in **Search**. Use natural language with **numbers and units**. You do not need a special command.
### Resistor power & rating
```
100Ω resistor at 12V — is 0.25W rating enough?
```
```
What power does a 10Ω resistor dissipate at 500mA? Margin vs 0.125W?
```
```
1206 0.1W at 3.3V through 330Ω — pass or fail?
```
### LDO / linear regulator thermal
```
Rough estimate: how much heat does a 3.3V LDO drop from 12V at 200mA?
```
```
12V to 3.3V LDO at 400mA, Ta 25°C, θJA 50°C/W — will Tj exceed 125°C?
```
```
MIC29302: 3.3V in, 2.5V out, 1.5A — thermal check at 75°C ambient
```
### Mixing part context with the calc
```
For TPS7A3301 in SOT-23, 5V to 3.3V at 300mA — Pd and Tj estimate
```
```
Compare 0.25W vs 0.5W for this divider: 12V, Rtop 10k, Rbot 3.3k
```
If the question is ambiguous, answer in chat first—then use **Try different inputs** in the panel instead of re-searching.
## Intelligent UI — tune parameters locally
After the written answer:
1. Open the audit panel (for example **Resistor power rating audit** or **Power dissipation & junction temperature**).
2. Use **Try different inputs (recalculates here only)** — sliders or fields for voltage, current, resistance, rating, θJA, etc.
3. Watch **margin**, **Pass/Fail** chips, and charts (such as predicted Tj vs limit) update **instantly** in the browser.
That local recalc does **not** spend another search credit. Use it for sweeps: higher ambient, worse θJA, or the next standard resistor wattage.
## What to trust
* Calculators use standard EE formulas shown in the answer—verify against your datasheet and application notes.
* Linear thermal models are **estimates**; real parts may current-limit, fold back, or hit thermal shutdown earlier than a simple Tj estimate predicts.
* For procurement and sign-off, cross-check critical limits on the **original datasheet** or [specification chat](/en-US/specification-chat).
## Related
* [AI Search](/en-US/ai-search)
* [How to write AI-understandable queries](/en-US/ai-query-writing)
* [Changelog — engineering calculator](/en-US/changelog)
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