Introducing Sigma: The GPA Calculator That Gets the Math Right
Why we built Sigma and how credit-weighted GPA calculations give you the accuracy your transcript actually uses.
Welcome to Sigma! We built this app because we noticed something broken with every GPA calculator on the App Store: none of them do credit-hour weighting correctly.
The Problem
Here's a scenario every student has experienced:
"My GPA app shows 3.8 but my transcript says 3.72—I don't understand why."
The reason? Most apps simply average your grades across classes. But that's not how GPA works. A 4-credit Calculus course impacts your GPA four times more than a 1-credit seminar.
The Sigma Formula
We're named after the Σ symbol in the actual GPA formula:
GPA = Σ(Grade Points × Credit Hours) / Σ(Credit Hours)
Let's see the difference with real numbers:
| Course | Grade | Credits | Quality Points |
|---|---|---|---|
| Calculus | A (4.0) | 4 | 16.0 |
| English | B+ (3.3) | 3 | 9.9 |
| PE | A (4.0) | 1 | 4.0 |
| Chemistry | B (3.0) | 4 | 12.0 |
Sigma (Correct): 41.9 ÷ 12 = 3.49
Simple Average (Wrong): (4.0 + 3.3 + 4.0 + 3.0) ÷ 4 = 3.58
That 0.09 difference might not sound like much, but when you're trying to maintain a 3.5 for grad school applications, accuracy matters.
What Makes Sigma Different
Per-Class Grading Scales
Not every professor uses the same grading scale. Some use A/B/C, others use A+/A/A-/B+. Sigma lets you set the scale for each course independently—no more forcing every class into the same mold.
6 Classes Free
Most competitors limit you to 3-4 classes before hitting a paywall. That's not even a full semester for most students! Sigma gives you 6 classes free—enough to track your entire semester before deciding if Premium is worth it.
Privacy First
Your grades are your business. Sigma:
- Syncs only through your personal iCloud
- Collects zero analytics or location data
- Has no ads, ever
- Works completely offline
What's Coming
We're just getting started. On the roadmap:
- Grade trend analytics
- Apple Intelligence integration for "What grade do I need?" questions
- Export to PDF for applications
Have feedback or questions? Reach out at support@bulpara.com.
"The Σ in your GPA, calculated correctly."