Practical guides, how-tos and comparisons to get the most out of our free online tools.
Four variables set depth of field, and subject distance dominates the other three. The exact formulas, a computed table, why the circle of confusion is a decision rather than a measurement, and what "full frame has less depth of field" really means.
Daniel Okonkwo · 13 min read
Each of the five fields has one job, and attribution rarely breaks on the mechanism — it breaks on inconsistent values. Here are the naming rules, the case-sensitivity trap, and the internal-link mistake that destroys the original attribution.
Camille Laurent · 12 min read
K is invitations per user times the conversion rate of an invitation — two small numbers multiplied. Below 1 the loop is a finite multiplier worth 1/(1−K), and cycle time decides which loop actually wins.
Camille Laurent · 11 min read
Abandonment rate is one minus completed over created — and the figure quoted everywhere is an average across wildly different shops. The useful work is turning a percentage point of checkout completion into money, then discounting it for returns.
Camille Laurent · 10 min read
These tools multiply followers by an assumed rate per thousand, which makes them a CPM model under another name — and every input behind that rate is an assumption they never show you.
Camille Laurent · 10 min read
Both methods write off exactly the same total cost. Only the timing differs — and timing is worth money. A full year-by-year schedule for one asset, the crossover year, the switch-to-straight-line convention, and the present value of the tax deferral computed at 8%.
Camille Laurent · 11 min read
FIFO and LIFO are assumptions about which cost you attach to a sale, not about which box leaves the warehouse. Worked through identical purchases and sales, they move cost of sales, inventory, profit and tax — but operating cash before tax is identical to the cent.
Camille Laurent · 11 min read
CCC = DIO + DSO − DPO. It is the number of days your cash is out of your hands, and it is the reason a profitable, growing business runs out of money. Worked end to end, with the negative-cycle case that makes suppliers your cheapest lender.
Camille Laurent · 10 min read
EOQ = √(2DS/H) balances ordering cost against holding cost. Its most useful property is how flat the cost curve is around the optimum — and its four failure modes are quantity discounts, lumpy demand, a finite replenishment rate, and the two inputs nobody can measure.
Camille Laurent · 11 min read
WACC = E/V × Re + D/V × Rd × (1 − T). The tax shield makes debt genuinely cheaper, and the cost of equity comes from CAPM — whose beta and equity risk premium are estimates that move the answer by whole percentage points, and the valuation by a quarter.
Camille Laurent · 12 min read
The quick ratio removes inventory because inventory is the current asset that may not convert. Two companies with an identical current ratio can be five times apart on the quick ratio — and both measures are still blind to the one thing that actually stops a company paying: timing.
Camille Laurent · 11 min read
EBITDA adds back the two costs that differ most between companies, which is exactly what makes it comparable — and exactly why it flatters anyone who owns a lot of equipment. Here is the same profit walked all the way down, and the maintenance-capex floor the measure never shows.
Camille Laurent · 11 min read