Which parts of a recipe take longer in a bigger batch?

No, and the answer is not a single multiplier either. Split the time into stages. Heating up doubles, because the burner delivers a fixed amount of energy and there is twice as much to warm. Reducing doubles, for the same reason. But the simmer in the middle does not change at all — it is a chemical process running at a temperature, and quantity is irrelevant to it. On a typical stew that leaves the total somewhere around forty percent longer rather than twice as long.

Why does a pot scale differently from a roast?

Because they are limited by different things. A roast in an oven is surrounded by heat and the constraint is how fast that heat conducts to the middle, which gives the square-cube law — time rises with mass to the two-thirds, so doubling is 1.59 times. A pot on a burner is not conduction-limited; it is limited by the watts coming off the ring, so doubling the contents genuinely doubles the heating. Using the roasting rule on a stockpot underestimates by about a fifth at double and over a third at quadruple.

Does the simmering time really not change?

Not for the reason people expect it to. What happens during a simmer is chemistry at a temperature — collagen hydrolysing to gelatin, starch gelatinising, cell walls in vegetables breaking down. Those reactions proceed at a rate set by how hot the food is, not by how much of it there is. What does change is how long it takes to reach that temperature in the first place, which is why the heating stage scales and the holding stage does not. Once the pot is at a simmer, a bigger pot simmers on exactly the same clock.

How full can I fill a pot?

About two thirds for anything that simmers, and less if it foams. Beyond that you cannot stir without slopping, the moment it catches it goes over the side, and the base is trying to heat a column of liquid deep enough that the top and bottom behave differently. A batch that needs more than that wants a bigger pot or, better, two smaller ones — splitting across two burners doubles the heat going in, so the heating stage that would have scaled up comes back down again.

Should I scale the salt?

Yes, straight, because salt seasons a mass of food and that mass has scaled. The reason people advise otherwise is not chemistry but arithmetic: a small imprecision in the original becomes a large one when multiplied, and salt is the one ingredient you cannot take back out. Scale it, but hold back the last quarter and season at the end by tasting. The same advice applies to anything strongly flavoured — chilli, vinegar, fish sauce — for the same practical reason rather than any principle about scaling.

What about the oil for browning?

That one genuinely does not scale with the food. Oil coats the bottom of the pan, so what you need depends on the width of the pan rather than how much you are cooking in it. Tripling a stew in the same pan needs the same oil; moving to a pan twice the area needs twice the oil regardless of quantity. Browning gets harder too — the same burner spread over a wider base means less heat per square centimetre, which is why big batches often need browning in shifts rather than all at once.

Why does my big batch come out thinner?

Because you probably stopped reducing on the recipe’s clock. Driving off water costs about 2,260 joules per gram, so three times the liquid needs three times the energy and three times the time on the same burner. Stopping at the original twenty minutes leaves two thirds of the intended reduction undone, and the sauce is thin. A wider pan helps a little at a gentle simmer because more surface is exposed, but at a proper boil the limit is the heat going in, not the area — so it is mostly a matter of allowing longer.

Is it faster to use two pots or one big one?

Two, usually, and by a large margin on the stages that scale. Each pot gets its own burner, so the total heat going in doubles and the heating and reduction stages come back to roughly the single-batch time rather than the doubled one. The simmer runs in parallel and costs nothing extra. Against that is the fiddle of managing two pans and the fact that they will not be identical. For anything much beyond double, splitting is usually the better answer.

Do these rules apply to the oven as well?

Only partly, and the difference matters. An oven roasting a single larger joint follows the square-cube law, because the limit is heat conducting to the middle. But a tray of the same food spread wider behaves differently again — a slab is governed by its depth, so more food across a bigger tray at the same depth cooks in about the same time. The one thing that is consistent across all of them is that time never scales in step with quantity, and assuming it does is wrong in every case.

How accurate are the burner figures?

They are floors rather than forecasts. The calculation assumes all the delivered energy goes into the food, which is never quite true — heat escapes to the room, the pot itself absorbs some, and a lid changes everything. Gas is the least efficient of the three by a wide margin because most of the flame goes around the pan rather than into it. Treat the figures as a sanity check on whether the recipe’s timings were ever plausible on your hob, not as a schedule to cook to.

Batch Cooking Calculator

Ingredients scale. Time does not, and the reason is that a pot is doing three different jobs limited by three different things. Bringing it up to temperature is limited by the burner. It delivers a fixed number of watts, so three times the contents takes three times as long — twelve minutes becomes...

This page is for pots — stews, sauces, soups, braises. For a single larger joint in the oven the rule is different and the cooking time adjuster handles it, because a roast is limited by heat conducting inward while a pot is limited by the burner underneath it.

THE BATCH

RECIPE SERVES

YOU WANT

THE RECIPE'S OWN TIMINGS

HEAT UP (MIN)

SIMMER (MIN)

REDUCE (MIN)

RECIPE VOLUME (L)

YOUR POT (L)

ALLOW ABOUT

2 hr 21 min

Multiply every ingredient by 3.00. The clock does not follow: heating and reducing stretch because the burner can only deliver so much, while the simmer stays exactly where it was. Scaling the whole thing would have told you 3 hr 51 min.

INGREDIENTS

×3.00

TIME

×1.83

WAS

1 hr 17 min

The 45 min simmer does not change, and that is most of what you save. Collagen turning to gelatin, pulses softening, flavours settling — all of it runs at a temperature rather than at a quantity, and a fuller pot does not slow it down. Scaling that stage along with everything else would have added 1 hr 30 min for nothing.

Do not use the roasting rule here. A joint in the oven scales with mass to the two-thirds, so ×3.00 would be ×2.08 on the clock. A pot is different: the burner delivers a fixed number of watts, so twice the contents genuinely takes twice as long to heat and twice as long to reduce. Using the roasting figure on a stockpot underestimates the heating stages by 31%.

4.2L will not fit sensibly in a 5.7L pot. Filled past about two thirds a pot cannot be stirred without slopping, boils over the moment it catches, and heats unevenly because the base is doing all the work for a deep column of liquid. You want something nearer 6.3L — or split it across two pans, which also halves the heating time since each gets its own burner.

Stage	Recipe	×3.00	Scales?
heat up	12 min	36 min	scales with quantity
simmer	45 min	45 min	does not scale
reduce	20 min	1 hr	scales with quantity
Total	1 hr 17 min	2 hr 21 min	1 hr 30 min less than naive

What the ingredient multiplier does not cover. Almost everything scales straight — solids, liquids, salt with the mass it seasons. The exceptions are the ones that belong to the pan rather than the food: oil to coat a base scales with the width of the pan, not the quantity you are cooking, and a bigger pan browns less well per unit because the same burner is spread thinner. Season at the end rather than scaling by faith, because a small error in the original becomes a large one here.

THE CLOCK

Two of the three stages stretch and one does not. Heating and reducing are limited by how fast the burner can put energy in, so more food takes proportionally longer. Simmering is limited by chemistry, which does not care how much is in the pot. Treating the whole recipe as one number gets both halves wrong at once.

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HOW TO USE

1
Enter what the recipe serves and what you need, then split its time into the three stages it actually has. Most recipes bury these in the prose — "bring to the boil", "simmer for 45 minutes", "uncover and reduce".
2
Say whether this is a pot or a tray in the oven. The two obey different physics and the answer changes by a third or more at large multiples.
3
Give the recipe volume and your pot size. Filling past about two thirds is where batches boil over, and the fix is usually a second pan rather than a bigger one.
4
Open the burner check if you want to know whether the recipe timings were ever realistic on your hob. A weak gas ring and an induction plate differ by more than a factor of two.

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Last updated: August 1, 2026 · Heating and reduction treated as power-limited, simmering as a fixed chemical clock · Timings are a plan, not a substitute for tasting.