Home, DIY & motoring writer at Allin
Renovation, materials, measurements and the cost of running a car
Marco covers home improvement from the first measurement to the final coat, and the same arithmetic applied to a car: fuel and running costs, tyre and gear ratios, what depreciation actually takes each year. Practical guides on materials, costs and getting quantities right the first time.
Marco works from manufacturer data sheets and the trade standards a job is actually signed off against, and states the assumption behind every quantity — the waste allowance, the coat thickness, the annual mileage — so a reader can re-run the sum on their own figures instead of taking his on trust.
Ranked by how many pages of this site link to them, not by traffic.
Guides published under this byline in each section. Each link opens the section in full, across all writers.
· 6 min read
Two cats need three boxes, not two, and each should be one and a half body lengths long — 69 cm for an average adult. The litter figure that follows is larger than most people expect, and knowing why is the useful part.
· 6 min read
Length A + half B, width twice C, height D. The width rule is the one that fails people: a dog with 28 cm shoulders needs 56 cm of interior width, and no crate sold by weight rating tells you that.
· 13 min read
A calculator gives you an order of magnitude, and anything holding up a floor, a roof or people needs an engineer and a code check. Between those two facts there is a great deal worth knowing: which power of the span the deflection really follows, which loading case the tool assumes, and what L/360 is in fractions of an inch on a span you can measure.
· 11 min read
Sixty-three days is measured from ovulation, not from the mating. Counted from a mating date the same pregnancy spreads over two weeks, because sperm survive for days and a bitch is often mated more than once. What the calculator does with that, and where its window stops four days early.
· 11 min read
Resting energy scales with weight to the power 0.75, not linearly, which is why a chart that doubles the food for a cat twice the weight is 83 kcal a day over. Neutered against intact, indoor against outdoor, and the boundary the arithmetic must not cross.
· 12 min read
The depth follows the job: a bare display, a planted tank whose roots need room, an under-gravel plate. Then comes the number people are unprepared for — substrate is what puts a filled tank past what a piece of furniture can hold. Plus why fine sand compacts and coarse gravel traps waste.
· 13 min read
Every stocking calculator implements a length-per-volume rule, and waste output scales with body mass, not length. A fish twice as long makes nearly five times the ammonia. Run through the tool's five methods, the same tank comes back holding anywhere from 6 to 12 fish.
· 12 min read
The same 2,000 sq ft lawn at the same 1 lb of nitrogen per 1,000 sq ft takes 40 lb of a 5 percent blend or 4.3 lb of urea. Target nitrogen, not product — and read the bag count as shopping, not spreading.
· 13 min read
Two to four inches, and the right end of that window depends on the material: bark takes 3, screened compost takes 1 to 2, and gravel takes 1. Here is the depth trade-off, the settling nobody buys for, and the bag conversion where the count goes wrong.
· 12 min read
The same tank needs a 100 W heater in a warm flat and 300 W in an unheated room. The variable is the gap between the water and the room, which most rules of thumb drop entirely. Plus why two smaller heaters beat one big one, and where this calculator's recommendation stops being trustworthy.
· 11 min read
A two-bedroom home comes out at 56 boxes: 14 small, 21 medium, 12 large, 4 wardrobe, 5 dish. The total is the least useful number on the page — here is why the split matters, and what the count leaves out.
· 12 min read
A normal medium load in a high-efficiency machine works out at 37 ml. Load size swings that threefold; water hardness only 1.28-fold — and the tool's hardness input carries no units at all. Here are the scales and the conversions it leaves out.
· 17 min read
The 40 % limit for three or more conductors is not about whether they physically fit. It is about heat and about pulling them in without stripping the insulation — and the moment you use that space, the code takes current away from every conductor in the pipe.
· 15 min read
Twice the centre distance plus both circumferences is 36 % too long. Here is the real formula, how the two straight runs and the two arcs actually add up, how far the standard approximation drifts, and what to do with a figure that is not a catalogue length.
· 12 min read
Blocks, base gravel, drainage stone, geogrid and pipe, counted from the calculator's own output. Then the number nobody puts in a materials list: a saturated backfill pushes about 2.2 times as hard as a drained one.
· 13 min read
Section area times length times density, for nine profiles and fourteen metals. What the calculator returns, why one figure covers every carbon-steel grade, and the two places its geometry is not the merchant's geometry.
· 14 min read
Torque does not hold a joint together — preload does, and torque is a poor proxy for it. Here is where 90 % of your effort goes, what the K-factor really is, and why the same 37.84 N·m gives anything from 12.61 kN to 37.84 kN of clamping force.
· 12 min read
Bars each way, splice lengths in bar diameters, cover from the edge, and the exact tonnage to order. Run against the calculator, including the two places where its bar count comes out short.
· 13 min read
Count pieces first, then linear feet, then board feet. A 2×4 measures 1½ × 3½ inches but is billed on the full 2 × 4 — 34 % of what you pay for is sawdust. Worked from the calculator's real output, with the waste rule it actually applies.
· 15 min read
The break-even is a division, and the number underneath it moves more with where you charge than with which country you live in. Electricity and fuel prices from 2025 and 2026, the arithmetic in full, and the point at which an electric car stops saving anything at all.
· 15 min read
Three ways to put the same car on the drive, priced over five years at the same interest rate. The monthly payments rank the options in exactly the reverse order of what they cost — and the gap turns out to be a single, computable number.
· 14 min read
Put both on one axis — euros paid per kilowatt-hour a year of permanent saving — and the comparison becomes decidable. The same loft job costs 0.83 euros per kilowatt-hour a year in a 1965 house and 5.00 in a 2005 one, a factor of six. That, and not the age of the building by itself, is what inverts the verdict.
· 11 min read
Since June 2026 a French rooftop is paid 1.1 cents for an exported kilowatt-hour and avoids 25.61 cents by consuming the same one. That ratio of 23 to 1 makes the self-consumption rate — the variable almost every quote omits — worth more than the amount of sun falling on the roof.
· 11 min read
The percentages written into the deed decide who owns what for as long as the property exists — not who paid the deposit, not who pays the mortgage, not who does the renovation. In France, Spain and Italy the default is the same undivided co-ownership, and it comes with a right that surprises couples: either of you can force a sale.