Practical guides, how-tos and comparisons to get the most out of our free online tools.
Caffeine leaves by first-order kinetics, so what remains is the dose times one half to the power of elapsed time over half-life. The half-life is not a constant — it varies by multiples between people, and that is the whole story.
Sofia Nunes · 12 min read
Work out the internet speed your home needs by adding up Mbps per video stream, video call, and gamer, with clear examples.
Daniel Okonkwo · 4 min read
Half the monthly payment every fortnight is 26 half-payments a year — 13 monthly payments, not 12. On $300,000 at 6 percent it saves $74,436, of which $73,666 comes from the extra payment and only $771 from the fortnightly frequency itself.
Camille Laurent · 13 min read
GRM is price divided by annual gross rent — a screening ratio that ignores vacancy, costs, financing and tax. Two properties at $300,000 with $25,000 of rent both score 12.0, and one yields 5.83 percent while the other yields 3.75.
Camille Laurent · 13 min read
One point on a $300,000 loan costs $3,000 and saves $47.93 a month. The naive break-even is 63 months; discounted at 4 percent it is 71. And the number that decides it is not either of those — it is how long you keep the loan.
Camille Laurent · 15 min read
Both numbers are pure geometry — one is the volume a piston sweeps, the other a ratio of two volumes — and both are read as if they described power. Here is each derivation worked on real engines, and exactly what each number can and cannot support.
Marco Bianchi · 14 min read
The legal minimum exists to define an offence, not to describe a safe tyre. Tread does one job — getting water out of the contact patch — so its effect is near zero in the dry and decisive in the wet. Here is what the numbers say, and how to measure your own.
Marco Bianchi · 13 min read
Comparing a drive with a train ticket on fuel alone understates the car by a factor of five. Here is how to build the marginal cost of a trip, how to separate it from the fixed cost of ownership, and why both numbers are correct answers to different questions.
Marco Bianchi · 12 min read
Dollar-cost averaging means investing a fixed amount at regular intervals. Learn how it smooths out market volatility and removes the guesswork of timing.
Camille Laurent · 3 min read
A clear guide to percentages: find X% of a number, work out what percent one number is of another, and add or subtract a percentage — with worked examples.
Camille Laurent · 4 min read
A car's CO2 number and its fuel consumption number are the same measurement in different units, tied together by chemistry that you can do on paper. Here is the derivation, and then the three things the figure quietly leaves out.
Marco Bianchi · 11 min read
Average order value measures how much a customer spends per order. Learn the formula, why it matters for profitability, and proven ways to lift it.
Daniel Okonkwo · 3 min read