Calculators posts
The math and standards behind the calculators and converters: number systems, Unix timestamps, UTF-8, checksums and cryptography basics, compound interest and mortgage amortization, debt payoff strategies, TDEE and heart-rate zones, and how GPA scales and weighting work.
21 posts in the Calculators category.
Unit Circle Chart Explained: Sin, Cos and Tan at Every Angle
Every point on the unit circle is (cos θ, sin θ). The full chart with tangent, how to read any angle in three steps, and four patterns that make it easy to memorize.
0–60 in Under a Second: How Many G's Is That?
Turn any 0–60 time into g-force in three steps. The new Roadster's claimed 0.59 seconds is about 4.6 g, and here is why tires alone cannot get there.
What Is a Good GPA? Every GPA from 2.5 to 4.0, Explained
A 3.0 is good and a 3.5 is strong. How every GPA from 2.5 to 4.0 compares with the 3.11 national average, in high school and in college.
How to Convert a Decimal to a Fraction (and a Fraction to a Decimal)
Write the decimal over 10, 100 or 1,000, then simplify: 0.75 = 3/4. Repeating decimals, mixed numbers, simplifying and fractions back to decimals, step by step.
How to Calculate Your Grade: Points, Weighted Categories and the Final Exam
Divide points earned by points possible, or weight each category and add them up: 172 out of 200 is 86%. Plus the formula for the score you need on your final.
GPA Scale Chart: Letter Grades, Percentages, and What Your GPA Means
The full 4.0 scale with letter grades and percentage ranges, what common GPAs mean, and how to convert percentages correctly.
Weighted vs Unweighted vs Cumulative GPA: How Each Is Calculated
Unweighted GPA ignores difficulty, weighted GPA adds honors and AP points, cumulative GPA combines every term. Worked examples for each.
X.509 Certificates Explained: Anatomy of the Web's Identity Layer
Every HTTPS handshake, every code-signing check, every TLS-secured email rests on X.509. We dissect the fields, extensions, chain of trust, and what each section actually does.
TDEE, BMR, and Macros Explained: The Math Behind Calorie Calculators
Every fitness app guesses your calorie target the same way: BMR formula, activity multiplier, macro split. We open the black box and show what each variable actually means.
How Mortgage Amortization Actually Works (With the Math)
Why is most of your early payment going to interest? We work through the amortization formula step by step, build the schedule from scratch, and show what extra payments really do.
How Heart Rate Zones Work (And Why Karvonen Beats Plain Max-HR)
Most fitness watches use percent of max HR. Karvonen factors in your resting rate. We explain why that matters, what each zone actually trains, and how to set yours correctly.
Debt Snowball vs Debt Avalanche: Which Strategy Pays Off Faster?
The avalanche method always wins on math. The snowball method usually wins on follow-through. We weigh both, run the numbers on a $24,500 four-debt scenario, and explain why both methods exist.
Compound Interest, SIP, and 401(k): Three Ways Money Grows
Time in the market beats timing the market — but only if you understand the math. We compare lump-sum compounding, monthly SIP, and employer-matched 401(k) contributions.
What Is a Checksum and Why It Matters for Data Integrity
A checksum is a small number computed from a block of data that lets you verify the data has not changed. Here is why this simple idea underpins file downloads, network protocols, and storage systems.
How TLS and HTTPS Work: From Handshake to Encrypted Connection
Every HTTPS connection starts with a TLS handshake — a sub-second ceremony that establishes identity and agrees on encryption keys. Here is the full sequence in plain English.
Public Key Cryptography Explained Simply: Keys, Ciphers, and Signatures
The magic behind HTTPS, SSH, and PGP encryption is public key cryptography — a system where you can encrypt a message that only the intended recipient can decrypt. Here is how it works.
How Timestamps and Unix Epoch Work: A Developer's Complete Guide
Unix timestamps are just numbers — the count of seconds since January 1, 1970 UTC. But timezone handling, milliseconds vs seconds, and the 2038 problem all add complexity that catches developers off guard.
Binary, Octal, and Hexadecimal: Number Systems Every Developer Needs
Binary is not just for low-level programming — it shows up in bitmasks, permissions, color values, and network addresses. This guide makes number base conversion intuitive rather than mechanical.
How UTF-8 and Unicode Work: Text Encoding for Developers
Every string in your program is ultimately bytes. Understanding how Unicode maps characters to code points and how UTF-8 encodes those to bytes prevents a whole class of subtle bugs.
Encoding vs Encryption vs Hashing: The Key Differences Explained
Treating Base64 as encryption or MD5 as a secure hash are among the most common security mistakes developers make. This post draws a clear line between encoding, encryption, and hashing.
How Random Number Generation Works in Computing
Math.random() and /dev/urandom look similar but are fundamentally different. One is suitable for games, one for cryptography. Understanding why that distinction matters prevents serious security mistakes.