MegaCalc Blog
In-depth guides on engineering calculations, unit systems, time zones, currency, and the math behind the conversions you use every day. Each article states its publication or draft status and includes sources for further study.
GMT vs UTC: Why They Show the Same Time but Are Not the Same Thing
One is a place on the map, the other is the reference the map is drawn against. Why GMT and UTC match to the second and still must not be swapped.
13 min readtime-zonesstandardsCST vs CDT: Central Time's Two Abbreviations (And Three Zones Named CST)
Why Central Time is CST in winter and CDT in summer, what CT means, and why three different zones answer to 'CST'.
13 min readtime-zonesnorth-americaEST vs EDT: Eastern Time's Two Abbreviations and When Each Applies
One zone, two labels, a 34-week daylight window, and a three-letter collision with Australia that has broken more calendars than any other abbreviation.
14 min readtime-zonesnorth-americaMST vs MDT: Why Mountain Time Has Two Abbreviations (And Arizona Only One)
Why Mountain Time uses two abbreviations, why most of Arizona uses only one, and why a drive across Navajo County can cross six time changes in 100 miles.
14 min readtime-zonesnorth-americaShaft Design Calculation Explained: Bending + Torsion
How to size a rotating shaft under combined bending and torsion using the ASME distortion-energy method — with allowable-stress selection, stress concentrations, and a fully worked numeric example.
12 min readmechanical-engineeringmachine-designstress-analysisRadiation Heat Transfer Explained for Engineers
How thermal radiation actually works — the Stefan-Boltzmann law, emissivity, the absolute-temperature trap, and when radiation overtakes convection and conduction.
12 min readmechanical-engineeringthermodynamicsheat-transferWhat Is a Newton? The SI Unit of Force Explained
What a newton actually is, how big one feels, how it relates to pounds-force and kilograms-force, and why confusing mass with weight is the classic mistake.
11 min readphysicsunitsmechanical-engineeringkN/m Line Loads Explained for Structural Engineers
What a kN/m distributed load really is, where it comes from, how it sets beam reactions and moments, and the unit conversions engineers conflate — line load vs linear mass density.
12 min readcivil-engineeringmechanical-engineeringunitsBytes vs Megabytes: Why 1 MB Isn't Always 1,000,000 Bytes
Sometimes 1 MB means 1,000,000 bytes. Sometimes it means 1,048,576. Here's why both are correct, and how to tell which one you're looking at.
9 min readdata-storagecomputer-scienceunitsMegapascals (MPa) Explained for Mechanical Engineers
Why mechanical engineers around the world reach for megapascals first — and how to keep your stress, pressure, and strength numbers straight.
10 min readmechanical-engineeringunitsstress-analysisHow to Read Steam Tables: A Mechanical Engineer's Guide
From v_f and h_fg to two-way interpolation and quality calculations — the practical reference engineers actually use at the desk.
11 min readthermodynamicsmechanical-engineeringReading Metric Construction Blueprints in the United States
When the architect drew it in millimeters but the lumber yard sells it in inches, here is how to read the drawing and order the right materials.
10 min readconstructionunitscivil-engineeringWhy Indonesia Uses WIB (Western Indonesian Time) and Not GMT+7
Three zones, one country, no daylight saving. A practical guide to WIB, WITA, and WIT for engineers, remote workers, and anyone scheduling meetings with Indonesia.
9 min readtime-zonesgeographyPDT vs PST: Why Pacific Time Has Two Abbreviations (And When to Use Each)
Why Pacific Time uses two letters in winter and a different two in summer, what 'PT' really means, and the small mistakes that cost you a missed call.
10 min readtime-zonesnorth-americaCommon BMI Interpretation Mistakes (And What the Number Actually Tells You)
BMI was invented in 1832 to study populations, not patients. Here is what the categories really mean, where they break down, and what to look at alongside them.
10 min readhealthanthropometryPressure Unit Selection Guide for HVAC Engineers (PSI, kPa, MPa, Bar, inH2O, inHg)
Refrigerant pressures in psi, fan static in inches of water, building leakage in pascals, evacuation in inches of mercury. Here is when to use each — and how to convert without errors.
11 min readhvacmechanical-engineeringpressureHow Engineers Choose Between PSI, Bar, kPa, and MPa
Four units, one quantity, very different conventions. When to spec each, how to convert without errors, and the gauge-vs-absolute traps that bite engineers in cross-market work.
9 min readmechanical-engineeringpressureunitsConvert Cooking Measurements Without Ruining Your Recipe (Cups, Tablespoons, mL, Grams)
Why a cup is not a cup, a tablespoon is not always 15 mL, and a cup of flour can weigh anywhere from 120 to 150 grams. Convert recipes correctly the first time.
9 min readcookingeveryday-conversions