Baking Pan Size Conversion Chart: How to Scale Recipes for Different Pans

Baking pans are converted by comparing their area, the flat surface the batter covers, not a single dimension like diameter or side length. A round pan’s area is π × radius². A square pan’s area is side × side. A rectangular pan’s area is length × width. Once you know the area of the pan a recipe was written for and the area of the pan you actually own, dividing the new area by the original area gives the exact multiplier to apply to every ingredient.

This chart lists the area of the round, square, rectangular, and loaf pans most home bakers own, walks through that scaling-factor formula with full arithmetic, and covers the two things area alone does not settle: how deep the batter ends up sitting, and how long the pan needs in the oven.

Why One Dimension Alone Misleads You

A 9-inch round pan looks only a little bigger than an 8-inch round pan, one inch across. But the diameter is not what holds the batter; the area of the base is. Going from 8 inches to 9 inches increases the diameter by 12.5% (9 ÷ 8 = 1.125), yet it increases the area by about 26.6%, because area grows with the square of the radius, not with the radius itself. King Arthur Baking makes the same point in its guide to pan size, warning that confusing diameter with volume is a common and costly mistake when swapping pans.

That gap between “looks similar” and “holds 26.6% more” is why a cake baked in the wrong pan turns out too thin and overdone, or too thick and raw in the middle. The fix is arithmetic: calculate the area of the pan the recipe assumes, calculate the area of the pan on your counter, and compare the two numbers directly.

The Three Area Formulas

Nearly every home baking pan reduces to one of three shapes for the purpose of area math.

Round pans: area = π × r²

A round pan’s area is pi (π ≈ 3.14159) multiplied by the radius squared, where radius is half the diameter, the size stamped on the pan or measured straight across the top rim.

6-inch round pan: r = 3 in, area = π × 3² = π × 9 ≈ 28.3 in².

Square pans: area = side × side

A square pan’s area is one side multiplied by itself. No radius, no rounding, an exact figure.

8x8-inch square pan: area = 8 × 8 = 64 in². Exact, no estimation needed.

Rectangular pans: area = length × width

A rectangular pan’s area is length times width.

9x13-inch pan, the standard sheet-cake size: area = 9 × 13 = 117 in².

Common Baking Pan Sizes and Their Area

Round cake pans most often come in 6, 8, 9, and 10-inch diameters; square pans in 8x8 and 9x9; and 9x13 is the standard rectangular sheet size, according to the size chart published by Sally’s Baking Addiction. The table below gives the exact area of each, in both square inches and square centimeters (using 1 in = 2.54 cm exactly, so 1 in² = 2.54² = 6.4516 cm²).

Loaf Pans: 8½x4½ vs 9x5

Two loaf pan sizes cover most yeast bread and quick bread recipes: 8½x4½ inches and 9x5 inches. King Arthur Baking’s guide to choosing a bread pan notes that most yeast bread recipes are written for one of these two sizes, and that the choice affects both the rise and the crust.

8½x4½-inch loaf pan: area = 8.5 × 4.5 = 38.25 in².

9x5-inch loaf pan: area = 9 × 5 = 45 in².

The 9x5 pan has 45 − 38.25 = 6.75 in² more area, which is 6.75 ÷ 38.25 ≈ 0.176, about 17.6% more than the 8½x4½ pan. A dough written for the smaller pan and baked in the larger one spreads out and rises shorter; the reverse crowds the pan and can dome or overflow. Loaf pans also taper slightly toward the base and run deeper (commonly 2½ to 3 inches) than layer cake pans, so treat the area figure as a close approximation for shopping and scaling, not an exact volume.

8-Inch vs 9-Inch Round Pan: The Real Difference

This is the single most common pan mix-up, because the pans sit right next to each other on the shelf and look nearly identical.

8-inch round pan: r = 4 in, area = π × 4² = π × 16 ≈ 50.2654 in².

9-inch round pan: r = 4.5 in, area = π × 4.5² = π × 20.25 ≈ 63.6172 in².

Difference: 63.6172 − 50.2654 = 13.3518 in².

Percent increase: 13.3518 ÷ 50.2654 ≈ 0.2656, about 26.6% more area in the 9-inch pan, even though the diameter grew by only 12.5%.

If a recipe built for an 8-inch pan goes into a 9-inch pan without adjustment, the same amount of batter spreads over 26.6% more surface, so the cake bakes thinner, faster, and can dry out before the center sets. Run the recipe in reverse, from 9-inch into 8-inch, and the batter has nowhere to spread, so it mounds deeper, takes longer to bake through, and risks overflowing if the pan was already filled close to its limit.

8x8 Square vs 9x13 Rectangular: The Real Difference

8x8 square pan: area = 8 × 8 = 64 in².

9x13 rectangular pan: area = 9 × 13 = 117 in².

Difference: 117 − 64 = 53 in².

Percent increase: 53 ÷ 64 = 0.828125, about 82.8% more area in the 9x13 pan. As a scale factor, 117 ÷ 64 = 1.828, so a 9x13 recipe holds roughly 1.83 times what an 8x8 pan holds, nearly double.

That is a bigger jump than most bakers expect from “one pan is a bit longer.” Splitting a 9x13 recipe in half (a 0.5 multiplier) gets close to an 8x8 pan’s capacity but slightly undershoots it, since 0.5 × 117 = 58.5 in², a bit less than the 8x8’s 64 in². The exact factor for an 8x8, using the method in the next section, is 64 ÷ 117 ≈ 0.547, so use about 55% of the 9x13 recipe rather than an even half.

Converting Pan Sizes from Inches to Centimeters

One inch equals exactly 2.54 centimeters. For area, square that figure: 1 in² = 2.54² = 6.4516 cm². Either convert the dimensions first and then multiply, or calculate the area in inches and multiply the result by 6.4516; both routes land on the same number.

8-inch round pan in centimeters: diameter = 8 × 2.54 = 20.32 cm, radius = 10.16 cm, area = π × 10.16² = π × 103.2256 ≈ 324.3 cm². Cross-checked the other way: 50.2654 in² × 6.4516 ≈ 324.3 cm², the same result.

9x13 pan in centimeters: length = 9 × 2.54 = 22.86 cm, width = 13 × 2.54 = 33.02 cm, area = 22.86 × 33.02 ≈ 754.8 cm². Cross-checked: 117 in² × 6.4516 ≈ 754.8 cm², matching again.

This matters most for recipes written with metric bakeware, or when a pan’s label only gives centimeters. Convert to a common unit before comparing areas; never compare a centimeter figure directly against an inch figure.

The Scaling Factor Formula: Turning Area Into an Ingredient Multiplier

Once both areas are known, the formula is: scale factor = new pan area ÷ original pan area. Multiply every ingredient in the original recipe, flour, sugar, butter, eggs, liquid, all of it, by that same number.

Worked example A: a 9-inch round recipe, scaled to a 9x13 rectangular pan. Original area ≈ 63.6172 in², new area = 117 in². Scale factor = 117 ÷ 63.6172 ≈ 1.839, round to 1.84. A recipe that calls for 240 g of flour needs 240 × 1.84 = 441.6 g, about 442 g, in the 9x13 pan. A recipe that calls for 200 g of sugar needs 200 × 1.84 = 368 g.

Worked example B: a 9x13 recipe, scaled down to a single 8x8 square pan. Original area = 117 in², new area = 64 in². Scale factor = 64 ÷ 117 ≈ 0.547, round to 0.55. A recipe that calls for 400 g of sugar needs 400 × 0.55 = 220 g in the 8x8 pan. A recipe that calls for 3 eggs needs 3 × 0.55 ≈ 1.65 eggs, a case where rounding to a whole number (2 eggs, or 1 egg plus a splash of extra liquid) is more practical than the exact decimal; see how to halve, double, or triple a recipe for the full technique for scaling eggs and other awkward amounts.

Once the factor is set, apply it to the whole ingredient list at once rather than recalculating each line by hand. The recipe scaler does exactly that: enter each ingredient’s amount in grams, enter the scale factor calculated above as a custom multiplier, and every ingredient recalculates together, shown in both grams and cups. For single-ingredient conversions along the way, the grams to cups converter handles the cup equivalent of any scaled gram amount.

Area Gets You the Right Amount, Not Automatically the Right Depth

Matching area tells you how much batter to use to keep roughly the same fill depth the original recipe intended, assuming the new pan has a similar wall height to the old one. It does not check whether that depth actually fits the new pan’s shape.

Real bakeware does not all share the same depth. A standard round layer cake pan runs about 2 inches tall. A loaf pan is closer to 2½ to 3 inches. A jelly-roll or sheet pan is often just 1 inch deep, and a Bundt pan can run 3 to 4 inches. If the area-scaled batter volume for a recipe would fill a 2-inch round pan two-thirds full, that same volume poured into a 1-inch-deep sheet pan does not fit at a safe depth: it has to spread further than the pan allows, run over the rim, or get split across two pans.

The opposite problem shows up with narrow, deep pans. Pour an area-scaled amount of batter into a Bundt or loaf pan and it sits noticeably deeper than it would in a wide layer pan, even though the area math is correct. A deeper pool of batter takes longer for heat to reach the center, so the outside can finish, or even overbake, well before the middle sets.

Area conversion is the right first step for the ingredient list. Depth is the second check: compare the wall height of the new pan with the original, and if the shapes are very different (round to sheet pan, round to loaf pan, round to Bundt), expect to adjust time and possibly temperature as well, which is a separate calculation from the scale factor. For more on why small measuring and handling differences compound in baked goods, see the science of why baking needs precision.

Baking Time Is Not Scaled by the Same Factor

The scale factor that corrects ingredient quantities does not correct baking time. Time depends on how deep and how dense the batter sits in the pan, not on how many grams of flour went into it.

As a general pattern: a smaller or deeper pan holding the same recipe generally needs a longer bake at a slightly lower oven temperature, so the center has time to cook through without the outside burning first. A larger or shallower pan generally needs a shorter bake at the same temperature, or slightly higher, since the batter is thinner and heat reaches the center faster. Neither adjustment follows the scale factor. Doubling the ingredients (a 2.0 scale factor) does not mean doubling the bake time.

Treat the recipe’s original time as a starting point and watch the pan, not the multiplier. Use a toothpick inserted in the center, an internal temperature check, or visual cues (edges pulling from the pan, a springy top) to judge doneness, and start checking earlier than the original time when the new pan is shallower, later when it is deeper.

Don’t Fill Past Two-Thirds: Why Overfilled Pans Overflow

Cake batter expands as it bakes: trapped air, steam, and gas from baking powder or baking soda all push the batter upward. Without headspace to expand into, it spills over the rim, bakes unevenly, or collapses after it domes too high, too fast.

King Arthur Baking’s pan-size guidance recommends filling most creamed-butter and one-bowl oil-based cake batters between half and two-thirds full, and Tasting Table describes the two-thirds-full rule as the standard guideline bakers reach for, with airier sponge and chiffon batters sometimes filled to only about half, since they rise more dramatically. Treat two-thirds as a practical ceiling, not a rigid law: it varies a little by batter type, but it is a useful check before the pan goes in the oven.

This is also a check on the scale factor, not just a baking tip. If a scaled batch of batter would fill the target pan past that two-thirds line, do not force it into one pan. Split the batter across two pans of the same size instead, or move up to a larger pan and recalculate the factor again using its area. Running the area math first, then checking the fill line before baking, catches an overflow before it happens rather than after.

Putting the Numbers to Use

The core steps stay the same for any pan swap: identify both areas using π × r² for round, side × side for square, or length × width for rectangular pans, divide the new area by the original to get the scale factor, and apply that single number to every ingredient. Then treat the result as a starting point for depth and time, not a finished answer. Check the new pan’s wall height against the two-thirds fill guideline, and judge doneness by the cake, not by the clock.

For the ingredient side of a pan swap, the ingredient density guide lists grams-per-cup figures for the flours, sugars, and fats most recipes call for, useful once the scale factor tells you how much more or less of each you need. To compare gram amounts across a wider set of baking staples in one place, the grams to cups conversion chart and the site’s printable charts cover the same ground for the ingredient list itself.