Clay Weight Calculator for Pottery

Calculating the right amount of clay for your pottery pieces is essential for successful throwing. Many newer potters do not yet have enough experience to know how much clay to use for a given piece. And even experienced potters will sometimes over or under estimate the amount of clay needed for a piece if it is something that they have not made before. Our clay weight calculator uses precise mathematical formulas to determine the exact clay weight needed based on your piece dimensions, clay shrinkage, and skill level.

Never Guess Your Throwing Size Again

One of the biggest challenges in pottery is knowing how large to throw a piece to achieve your desired final size. Our calculator solves this problem by working in both directions: enter your desired final dimensions and get the exact green (wet) dimensions to throw, or enter your throwing dimensions to see what the final fired size will be. No more "teeny tiny pieces" or oversized mugs!

Perfect for Planning Your Pottery Projects

Whether you're making a set of matching mugs, planning a large bowl, or creating functional dinnerware, our calculator ensures you throw each piece to the perfect size. Enter your target final dimensions and get the exact throwing dimensions needed, accounting for your clay's specific shrinkage rate. This eliminates the guesswork and helps you create consistent, properly-sized pottery every time.

Understanding Clay Shrinkage in Pottery

Clay shrinkage is the percentage that clay reduces in size when fired. Most stoneware clays shrink 10-15% during the firing process. This means if you want a final piece that's 6 inches tall, you need to throw it about 6.7 inches tall when wet. One of the biggest mistakes that new potters make is to not account for this shrinkage when throwing a piece. They throw the piece at the desired final height, but then when they fire it, they end up with a teeny tiny piece that is not the size they wanted. I was notorious for thowing "large mugs" but then ending up with a small toy tea cup. Don't be like me!

Clay Density and Weight Calculations

Not all clay bodies weigh the same—each type of clay has its own density, which directly affects how much raw clay you’ll need for a project. Stoneware, for example, typically has a density in the 1.6–1.8 g/cm³ range, making it a durable and versatile choice for functional pieces like mugs, bowls, and dinnerware. Porcelain is much denser, usually between 2.3–2.5 g/cm³, which gives it that smooth, refined surface and even a translucent quality when thin. Because of its density, porcelain requires noticeably more clay by weight to create the same size form as stoneware. On the other end of the spectrum, earthenware is lighter, generally around 1.5–1.7 g/cm³. It’s more porous and often used for lower-fired decorative pieces, such as terra-cotta.

Our calculator factors in these density differences, so when you enter your project’s dimensions, it can provide a more accurate clay weight estimate based on the specific material you’re working with. This way, you’re not only measuring by size but also by the true physical properties of your chosen clay.

Beginner vs Advanced Clay Weight Needs

Beginners typically need at least 10-15% more clay than calculated due to practice, mistakes, and learning. Advanced potters can work more efficiently and may need 5-10% less clay than the base calculation. It is a lot easier to begin with more clay for a piece than it is to add it later. Excess can always be trimmed off. So beginners, prepare more clay than you think you need!