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· 11 min read
Before any grant, the price of electricity divided by the price of gas sets a seasonal efficiency the heat pump must beat just to break even on running cost. In late 2025 that number was 1.53 in Portugal and 2.79 in Germany — and on old radiators a German heat pump can cost more to run than the boiler it replaced.
· 12 min read
Most of what buyers call the notary's fee is transfer tax, and it is fixed by a department, an autonomous community or a national scale. The genuinely negotiable share is small, and knowing which line it is on is worth more than haggling over the rest. Portugal added a flat 7.5 % rate for non-resident buyers in May 2026.
· 10 min read
Furnishing a flat moves it from one tax code to another: 50 % of the rent is written off instead of 30 %, and a landlord on the full regime can depreciate the building. Since 15 February 2025 that depreciation is clawed back on sale, which changes the whole calculation.
· 16 min read
There is no single towing capacity. There are four or five separate limits, and the one that binds is rarely the tow rating on the brochure — it is usually the vehicle's own weight budget, quietly consumed by the people sitting in it.
· 8 min read
A compost heap wants 25 to 30 parts carbon to one part nitrogen by dry weight. Cardboard is 350:1, grass clippings 17:1. Here is the materials table, one mix worked through to 28:1, and why the volume rule of thumb is a different measurement entirely.
· 15 min read
Engine rpm reaches the road through one unbroken multiplication chain, and the last link is the tyre. Change the tyre's rolling circumference and the speedometer goes wrong by exactly that percentage — in a direction the law cares about.
· 8 min read
A 13 by 17 ft room is 221 square feet of floor, but carpet comes off a 12 or 15 ft roll, so you buy 255 square feet and bin 34. Here is how to work out the order quantity your supplier will actually invoice.
· 17 min read
Total stopping distance is two distances added together, and they follow different laws — one grows with speed, the other with speed squared. That single fact explains why doubling your speed roughly triples the distance.
· 8 min read
Length × width × average depth gives 21,065 gallons for a 32 by 16 ft pool. But average depth only means (shallow + deep) ÷ 2 when the floor slopes evenly, and most pools do not. Here is every shape formula and the correction.
· 8 min read
A 100 percent grade is 45 degrees, not vertical. Percent is rise ÷ run × 100, the angle is the arctangent of the same fraction, and the two are not proportional. Here is the conversion table and the three ways people get it wrong.
· 7 min read
A 750 ml bottle pours five glasses, and guests average about one drink per hour. Everything else is arithmetic — here it is for 50 to 250 guests over three, four and five hours, with an honest range rather than a single number.
· 9 min read
A conventional wet brine is 5 to 6 percent salt by weight of the water and you pull the meat out on a timer. An equilibrium brine is 1 to 2 percent by weight of the meat and water together, and it cannot over-salt. Those are different numbers doing different jobs.
· 7 min read
Multiply fresh yeast by 0.4 for active dry and by 0.33 for instant. Those two numbers are the whole chart, they are King Arthur's professional figures, and they are approximate — here is how far, and what else changes when you swap.
· 7 min read
Flour is 100 percent and everything else is measured against it. That one convention lets the same recipe scale from a single loaf to a bakery batch without a single new calculation — and yes, the percentages are supposed to add up to more than 100.
· 6 min read
10-20-10 does not mean 10 percent phosphorus. The second and third numbers are oxides, so a 50 lb bag holds 4.4 lb of actual phosphorus, not 10. Here is what each number really measures and how to turn it into a rate.
· 7 min read
A 110 in rise divided by a 7 in target gives 15.7 risers. You round to 16 and divide again, landing on 6 7/8 in. Here is the whole method, and why the building codes do not agree with each other.
· 7 min read
Drop 25 °F and cut the time by about a fifth — then adjust for what the food is and how full the basket is, because those two change the answer more than the rule does.
· 6 min read
Temperature sets doneness, thickness sets time, and time at temperature is what makes food safe. Those are three different clocks, and most charts print only one of them.
· 6 min read
A full schedule from feeding the starter to slicing the loaf, and the one variable that moves every time on it. Five hours of bulk at 75 °F becomes about seven and a quarter at 68 °F.
· 3 min read
Grams measure weight and milliliters measure volume, so converting between them depends on density. Water is 1 gram per mL, but flour, sugar, and oil are not. Here is how to convert correctly.
· 4 min read
Work out the concrete for setting fence posts: hole volume minus the post, converted into bags of ready-mix, with the rule of thumb for hole depth and width.
· 4 min read
Doubling a recipe is more than multiplying by two. Learn the scale factor, which ingredients to scale carefully — spices, salt, leavening — and why bake time and pan size do not simply double.
· 4 min read
Count wallpaper rolls correctly when the pattern repeats: how repeat length creates waste on every strip, and how to turn wall area into the number of rolls to buy.
· 3 min read
A US cup holds 8 fluid ounces, a pint 16, a quart 32, and a gallon 128. See the full chart with milliliter equivalents and why US and UK ounces are not the same.