How do I scale, measure and convert this recipe?

It is a way of writing a recipe where flour is always 100% and every other ingredient is expressed as a percentage of the flour weight — not of the total. A formula written as 100% flour, 70% water, 2% salt and 0.7% instant yeast scales to any batch size without arithmetic: 1000 g of flour means 700 g of water, 20 g of salt and 7 g of yeast. Because the percentages add up to more than 100%, a dough at those numbers weighs 1727 g in total, which is where the confusion usually starts.

Divide, do not subtract. The divisor is 1 plus the sum of every percentage other than flour, written as a decimal. At 70% hydration, 2% salt and 0.7% yeast the divisor is 1.727, so a target of 900 g of dough needs 900 ÷ 1.727 ≈ 521 g of flour. Then apply the percentages to that flour figure. This is how you size dough balls: for a 250 g pizza ball at 60% hydration with 2% salt, 3% oil and 1% yeast, the divisor is 1.66 and the flour is about 151 g.

Below 60% you get a stiff, easy-to-knead dough with a tight crumb — bagels, pretzels and most pizza. From 60 to 70% is the standard, forgiving all-purpose range for sandwich loaves and pan breads. From 70 to 80% is artisan territory with an open crumb that needs stretch-and-folds instead of kneading. Above 80% the dough is slack and sticky, worked with wet hands and a scraper, and above 90% it stops being shapeable at all — that is no-knead and ciabatta.

A starter is not a seasoning, it is flour and water that already went into the mix. At 100% hydration it is exactly half flour and half water by weight, so 200 g of starter contributes 100 g of flour and 100 g of water. Your total flour is the flour you add plus that hidden 100 g, target water is total flour × target hydration, and the water you actually pour in is that target minus the 100 g the starter brought. Salt is a percentage of total flour too, starter included — this is the single most common sourdough math mistake.

Fermentation follows a Q10 of about 2: yeast activity roughly doubles for every 10 °C (18 °F) increase, and halves for every 10 °C drop. Starting from a reference of one hour at 25 °C (77 °F) with 2% fresh yeast, the estimate is base × 2^((25 − T)/10) × (2 ÷ your dose in fresh-yeast terms). One percent of instant yeast counts as 3% fresh, and 1% of active dry counts as 2.25%. A dough at 68 °F with half the reference yeast will take roughly three times as long as the same dough at 77 °F with the full dose.

No. By weight, 1 g of instant yeast is worth about 3 g of fresh yeast, and 1 g of active dry is worth about 2.25 g of fresh. So a recipe calling for 30 g of fresh yeast needs about 10 g of instant or 13 g of active dry. Active dry also wants to be rehydrated in warm liquid first, while instant can go straight into the flour. Getting this conversion wrong is the usual reason a loaf either does nothing for four hours or over-proofs and collapses.

°C = (°F − 32) × 5/9 is the exact conversion. Gas Mark follows a linear British standard where °C = Gas Mark × 14 + 121, so Gas Mark 4 is 177 °C or 350 °F, and Gas Mark 7 is 219 °C or 425 °F. Round the Gas Mark to the nearest quarter — the dial has no more resolution than that. Below Gas Mark 1 (135 °C / 275 °F) the scale runs in quarters: ¼, ½ and ¾ cover the very low range used for slow roasting and meringues.

Yes — drop it by 25 °F (about 14 °C) and expect to shorten the time by roughly 25% as well. A moving-air oven transfers heat far more efficiently, so a recipe written for 400 °F conventional should be set to 375 °F on fan. Cakes and custards care the most; roasted vegetables and bread care the least and often benefit from the extra convection. Separately, most home ovens run 25 °F away from their dial in one direction or the other, which an oven thermometer will tell you in a single bake.

It depends entirely on density, which is why weight beats volume. One level teaspoon holds about 6 g of fine table salt, 4.5 g of coarse or sea salt, but only 2.8 g of flake salt — swapping salts by volume can change the seasoning by more than half. Sugar is about 4 g, all-purpose flour about 3 g, baking soda 4.8 g, baking powder 4 g, cocoa 2.6 g, cinnamon 2.6 g and dried oregano only 1 g. All of those assume a level spoon; a heaped one carries 50–100% more.

A US Large egg weighs 57 g in the shell. The shell is about 9% of that, the white about 58% and the yolk about 31%, so a Large egg gives roughly 33 g of white and 18 g of yolk, or 52 g of edible egg. Scale from there: Medium is 50 g, Extra Large 64 g and Jumbo 71 g in the shell. When a recipe needs half an egg — which happens constantly when scaling — beat a whole one and measure out half by weight or volume, since a beaten Large egg is about 3 tablespoons.

Because leavening does not scale linearly. A doubled batter is deeper and wider, so it holds gas better, and doubling the baking powder gives a bitter, soapy taste followed by a rise-then-collapse. Professional guidance caps the increase at roughly 78% of the linear amount once you go past 1.5×. The calculator applies that cap automatically and leaves everything else at the straight scale factor. When scaling down instead, the risk flips: below a quarter teaspoon, volume measuring loses so much accuracy that a gram scale becomes the only reliable option.

Steam, in almost every case. Boiling leaches water-soluble vitamins — C, B1 and folate especially — into water most people pour down the sink, while steaming keeps them in the food. Times are broadly similar: broccoli 4–6 minutes steamed against 5–8 boiled, green beans 5–8 either way, cubed potato 15–20 steamed against 12–18 boiled. Corn on the cob is the notable exception, going faster in boiling water. If you do boil, keep the liquid for a soup or sauce and you recover most of what was lost.