A recipe for 4 that you want to cook for 6. Or for 2 because you're eating alone. Or for 16 because you're hosting a birthday. Scaling sounds like simple multiplication, but anyone who's tasted a doubled curry that turned out too salty, or a recipe for 12 that ended up too liquid, knows there's more to it. This guide teaches you when linear math works and when to use judgment.

The math of scaling

Basics: if a recipe serves 4 and you want to cook for 6, the scale factor is 6/4 = 1.5. Multiply each ingredient by 1.5:

400g pasta → 600g
2 onions → 3 onions
1 can of tomatoes (400g) → 600g (1 can + half a can)
200ml cream → 300ml

Simple, until it isn't.

What scales linearly (almost always)

Main ingredients

Proteins — meat, fish, tofu, beans
Carb bases — rice, pasta, potatoes
Vegetables — as an ingredient

Liquids (in stews)

Stock, water, wine, soy sauce in stews and sauces usually scale well

Fats (oil, butter)

For searing you can scale slightly conservatively (70-80% linear is often enough)
For baking linear is fine

What does NOT scale linearly

Salt

Always taste when scaling a recipe. Our perception of salt isn't linear with quantity
Start with 80% of the calculated amount, add more if needed
Salt in multiple stages — build flavor during cooking rather than dumping it all in at the end

Herbs and spices

Some herbs scale linearly, others get overwhelming:

Linear OK: parsley, basil, dill (fresh herbs)
Careful: cinnamon, cardamom, curry powder, oregano — start at 75%
Very careful: chili flakes, cayenne, raw garlic — start at 60-70%

For big scale-ups (4x, 6x), err on the conservative side and adjust upward. You can't pull seasonings back.

Leavening in baking

This is the pitfall in baking:

Baking soda and powder — don't scale exactly linearly due to chemical dynamics
Yeast — when doubling, don't double; use about 1.7x (rise time changes)

For baking > 2x scaling: find a dedicated larger recipe, don't just double.

Cook times and temperatures

This surprises many:

Stews and soups — 30-50% longer cook time when doubled, not 2x
Oven dishes — usually 15-30% longer, depending on depth of the dish
Roasting — weight-dependent. 2x as thick meat needs 1.5x as long, not 2x
Oven temperature — can be slightly lowered (10°C / 20°F) for longer cook time on larger mass

Surface area (the pan problem)

If you have 2x the quantity, you often need 2x the surface:

Searing — sear in one pan twice, or use two pans at once
Roasting — 2x ingredients = 2x sheet pans. Overcrowded pans steam instead of roast
Boiling pasta — bigger pot, more water. Otherwise pasta clumps
Cooking — wider pot when doubling, else it's slow to come up to heat

Common scaling mistakes

Blindly multiplying salt/spices — overwhelming flavors
Small pan for large quantity — steaming instead of searing
Not tasting during cooking — at larger quantities, mid-cook tasting is doubly important
Blindly doubling cook time — stews get dry
Scaling recipes for 1-2 up to 8+ — better to start with a recipe already for ~4

Scaling down to 1 or 2 servings

The other end: shrinking a family recipe from 4 to 1 or 2. Watch for:

Portions under 1 egg — in baking, hard to resolve. Use 1 egg for a double portion and freeze the second, or find a dedicated solo recipe
Small herb amounts — ¼ teaspoon is almost nothing; use your fingers to portion
Pan size — smaller pan needs less fat; adjust
Cook times get shorter — 20-30% shorter when halving

When not to scale

Some recipes aren't scale-friendly:

Baking > 2x — buy or find a new recipe
Fermentation recipes (sourdough, kimchi) — chemistry changes at large batches
Soufflés and delicate bakes — don't scale well
Some Asian stir-fries — often can't go to bigger pan; better to cook 2x in sequence

How Parsely scales automatically

Parsely calculates the scale factor based on your desired servings and adjusts all ingredient quantities. Important: Parsely scales linearly. For salt, spices, and cook times, your judgment stays essential.

What Parsely does automatically

Recalculates all quantities (with clean fractions — no "0.333 onion")
Keeps units consistent (250g stays in grams, not auto-converted to kg)
Preserves the recipe link so you can always check the original

What you do

Taste salt and spices
Adjust pans to quantity
Adjust cook times and oven temps at large scale

How Parsely supports this

Parsely's scaling is one click: adjust servings in the recipe and everything recalculates. For people who batch often or cook for large groups, this changes the whole workflow. Try Parsely for free and test with a recipe you know well — scale to 2x and see if the result matches your expectation.

How to scale recipes up or down without disasters