CalcRegistry
Blog
Guides, explainers, and tips to help you get the most out of our free calculators and converters.
How to calculate distance between two GPS coordinates
Step-by-step latitude and longitude distance using the Haversine formula. Decimal degrees, a worked Paris–Kraków example, atan2 vs arcsin, and what crow-flies km is (and is not).
How Long Does GLP-1 Weight Loss Actually Take?
STEP and SURMOUNT trial averages are not your finish line. How starting weight, dose titration, and plateaus change the month count on Ozempic, Wegovy, Mounjaro, and Zepbound.
Average American mortgage debt by state (2026)
Average mortgage balances by state from Experian (Q1 2025), plus national mortgage totals from the New York Fed (Q4 2025), FHFA conforming loan limits, and MBA delinquency figures.
Age difference vs age gap: same numbers, different conversations
How people use age difference vs age gap, what stays fixed on the calendar (and what doesn’t), and when plain date math is enough. Links to CalcRegistry’s age difference calculator.
Why planes fly in curves: the geometry of great-circle routes
Why do flight paths arc toward the poles instead of crossing oceans in a straight line? Great-circle distance, the Haversine formula, and the geometry of a sphere explained.
Social Security: the one retirement decision where waiting actually pays off
How PIA, claiming at 62 vs 70, and breakeven age fit together, with taxes, couples, and calculators to model your own benefit estimates.
BMR vs TDEE for Weight Loss: How Far Below Maintenance Should You Eat?
Where the cutting preset fits, when it doesn't, and why eating below your BMR usually backfires. A plain-English look at maintenance calories and sane deficits.
Astrophotography without star trails: the 500 rule, the NPF rule, and a practical ceiling
Why stars smear, how the 500 rule and NPF rule cap your shutter, what declination and pixel pitch have to do with it, and how to get a number you can use on your next clear night. Includes our free calculator.
What Going Back to the Office Really Costs (and How to Put a Number on It)
Employers keep revisiting hybrid and return-to-office plans. Here's how to see past the gas pump and count what commuting actually takes from your year, including time.
Sensor size and crop factor: why your 50 mm lens doesn't always feel like a 50
A practical look at crop factor, full-frame as a reference, and what really changes when you swap sensor sizes. Framing, depth of field, noise, and when the math matters in real shoots.