Practical guides, how-tos and comparisons to get the most out of our free online tools.
A mean of 100 with a standard deviation of 15 over 30 observations gives 100 ± 5.37 at 95 %. Going to 120 observations gives ± 2.68 — exactly half, because the sample size enters under a square root.
Lena Hoffmann · 3 min read
600 of transport plus ten nights at 90 and ten days at 60 is 2,100. The transport everyone shops for is 29 % of it; the daily lines nobody compares are 71 %.
Antonio Delgado · 3 min read
A venue of 6,000, extras of 4,000 and 100 guests at 120 each totals 22,000 — and 12,000 of that is a single multiplication nobody thinks of as a decision.
Antonio Delgado · 3 min read
82 seedlings from 100 seeds is an 82 % germination rate. Wanting 30 plants with a 10 % margin means sowing 41 — and the packet's percentage is not the one your windowsill will deliver.
Marco Bianchi · 3 min read
24 servings of 120 ml is 2,880 ml, or 2.88 litres. That is the volume in the glass, not the volume of ingredients — and the gap between the two is the reason batched drinks taste harsh.
Marco Bianchi · 3 min read
48 divided by 6 servings is 8. Neither the 48 nor the 6 is usually right, and the two errors push in opposite directions without cancelling.
Marco Bianchi · 3 min read
Making something for 12, selling it wholesale at a 40 % margin and letting the retailer take 55 % puts it on the shelf at 44.44 — 3.7 times its cost, with two reasonable-looking margins.
Camille Laurent · 3 min read
10,000 growing at 7 % a year becomes 19,671.51 after ten years — a rise of 96.7 %. The rule of 72 predicted 10.3 years to double, and it was right to within four months.
Camille Laurent · 3 min read
Current assets of 150,000 less current liabilities of 100,000 gives working capital of 50,000 and a ratio of 1.5. Whether that is comfortable depends on what the 150,000 is made of.
Camille Laurent · 3 min read
180,000 outstanding against 1,200,000 of annual sales is 54.75 days of collection and 6.67 turns a year. On thirty-day terms, that gap is a quarter of a million financed for free.
Camille Laurent · 3 min read
7,000 units made against a capacity of 10,000 is 70 % utilisation. The reflex is to call the other 30 % a loss; queueing theory says it is the reason the line still delivers on time.
Lena Hoffmann · 3 min read
At 85 % monthly retention the average customer stays 6.7 months and is worth 224. At 95 % they stay 20 months and are worth 373. The lifetime is a reciprocal, and reciprocals explode.
Lena Hoffmann · 3 min read