How Much Down Payment Do You Need to Buy a Home?
How to work out a down payment: typical percentages, the 20% PMI threshold in the US, and how the amount you put down changes your monthly payment.
Camille Laurent · 3 min read
Guides & tutorials
Practical guides, how-tos and comparisons to get the most out of our free online tools.
April 2, 2026
April 1, 2026
How Much Carbohydrate Do You Actually Need?
There is a small hard answer — the brain's glucose demand, published as 130 g a day — and a very large soft one. Above the minimum, carbohydrate need scales with training volume in grams per kilogram, not with a percentage.
Sofia Nunes · 14 min read
How to Calculate Your Liquidation Price on a Leveraged Position
The liquidation price follows directly from your leverage: at 10x a 10 percent move wipes you out. Here is the formula, the maintenance margin that moves it closer, and how to read the number before you open.
Camille Laurent · 4 min read
March 31, 2026
How Long Until You Are Sober? Zero-Order Elimination Explained
Alcohol leaves the body at a roughly constant mass per hour, whatever the concentration. That one property — zero-order elimination, unlike caffeine's exponential decay — explains why doubling the dose doubles the time, why nothing speeds it up, and why every estimate carries a wide error bar. With the Widmark relation worked through, and each market's legal limit stated separately.
Sofia Nunes · 16 min read
Cups to Grams for Baking: Flour, Sugar & Butter Charts
Why 1 cup of flour and 1 cup of sugar don't weigh the same, plus cup-to-gram charts for baking ingredients — because density matters.
Marco Bianchi · 3 min read
How to Compare the Cost of Living Between Two Cities
Use a cost-of-living index to turn a job offer in another city into an apples-to-apples salary — so you know if the move leaves you better or worse off.
Camille Laurent · 5 min read
March 30, 2026
Caffeine Against Sleep Pressure: What It Blocks, and What It Cannot
Sleep is regulated by two processes: a pressure that builds with every waking hour, and a clock. Caffeine acts on neither directly — it blocks the receptors that report the pressure. The pressure keeps building behind the block, which is why the crash arrives and why an afternoon dose costs that night's sleep even when you do not feel it.
Sofia Nunes · 13 min read
Birthstones and Birth Flowers, Month by Month
The full modern list of birthstones and birth flowers for all twelve months, where the list actually comes from, and why older references give different stones.
Antonio Delgado · 4 min read
Chinese Zodiac: The 12 Animals, Their Years and the New Year Trap
The twelve-year animal cycle, the years each animal covers, and why anyone born in January or early February is usually assigned the wrong one.
Antonio Delgado · 4 min read
March 27, 2026
Baby Growth, and What Crossing Centiles Actually Means
The WHO infant standard is prescriptive: it was built from healthy breastfed babies and describes how infants should grow. National references describe how they did grow. In the first year the two disagree by enough to move the same baby forty percentile points, with no change in the baby. Here is the size of the gap, and what the published thresholds for concern actually say.
Sofia Nunes · 14 min read
Where a Percentile Comes From: Which Population, Measured When
A percentile is a rank against a reference population, so the first question is never the arithmetic — it is which population, measured when. The same 5'11" man is the 38th percentile in one national dataset and the 86th in another, and the 91st against a reference of people born a century ago. Here is why, and what a z-score adds.
Sofia Nunes · 12 min read
How to Read Tire Size: What 205/55 R16 Actually Means
The numbers on your tire sidewall decode into width, aspect ratio and rim diameter. Learn to read 205/55 R16 and work out the real overall diameter.
Marco Bianchi · 4 min read