How do I convert cubic inches to fluid ounces for epoxy?

Divide cubic inches by 1.805 to get fluid ounces. Example: a 6×6×2 inch mold = 72 cubic inches ÷ 1.805 = 39.9 fl oz. Then add your waste buffer (10–15%).

How do I calculate epoxy volume for an irregular shape?

For truly irregular shapes, use the water displacement method: fill the mold with water and measure how much water it holds in fl oz — that's your epoxy volume (plus your waste buffer). Alternatively, use the custom volume input in our calculator.

Epoxy Volume Calculator — Cubic Inches to Fluid Ounces

Q: What is the volume formula for a cylindrical mold?

Volume = π × radius² × height. For a 4-inch diameter, 6-inch tall cylinder: π × 2² × 6 = 75.4 cubic inches ÷ 1.805 = 41.8 fl oz.

Q: Does epoxy shrink after curing?

Epoxy resins shrink 1–4% by volume upon curing, depending on the system. Most calculators and pour calculations do not account for this shrinkage since it's typically small and within the waste buffer range.

Volume is the foundation of every epoxy calculation. Whether you're filling a rectangular mold, a cylindrical vase, or a free-form casting, you need to know the exact volume before you can order materials. This guide covers the volume formulas for all common shapes, the critical cubic inches to fluid ounces conversion, and how to use the free calculator to get your Part A and Part B quantities instantly.

Get exact volume in fl oz, mL, liters, and gallons — plus your Part A / Part B mix split.

📐 Calculate Epoxy Volume ⟶

🔢 The Core Conversion

Cubic Inches to Fluid Ounces — The Key Formula

Epoxy volume is almost always discussed in fluid ounces (fl oz), but most project measurements are taken in inches. The conversion factor:

Fluid ounces = Cubic inches ÷ 1.805
(Because 1 fl oz = 1.805 cubic inches)

Example: A 10″ × 8″ × 1.5″ mold = 120 cubic inches ÷ 1.805 = 66.5 fl oz needed.

Cubic Inches	Fluid Ounces	Cups	Liters (mL)
10 cu in	5.5 fl oz	0.69 cups	163 mL
25 cu in	13.9 fl oz	1.73 cups	410 mL
50 cu in	27.7 fl oz	3.46 cups	820 mL
100 cu in	55.4 fl oz	6.93 cups	1,640 mL
200 cu in	110.8 fl oz	13.85 cups	3,279 mL
500 cu in	277.1 fl oz	34.6 cups	8,199 mL

📦 Shape Volume Formulas

Volume Formulas for Common Mold Shapes

Shape	Formula (cubic inches)	Example	Result
Box / Rectangle	L × W × H	8″ × 6″ × 2″	96 cu in = 53.2 fl oz
Cylinder	π × r² × H	4″ dia × 5″ tall	62.8 cu in = 34.8 fl oz
Sphere	(4/3) × π × r³	3″ diameter	14.1 cu in = 7.8 fl oz
Cone	(1/3) × π × r² × H	4″ dia × 6″ tall	25.1 cu in = 13.9 fl oz
Hemisphere	(2/3) × π × r³	4″ diameter	16.8 cu in = 9.3 fl oz

For r (radius): r = diameter ÷ 2. All measurements in inches. The calculator's Mold/Casting mode automatically selects the correct formula when you choose your mold shape.

🧊 Practical Examples

Real Project Volume Examples

Here are worked examples for the most common projects:

6″ × 6″ × 2″ box mold:
6 × 6 × 2 = 72 cu in ÷ 1.805 = 39.9 fl oz net. Add 10% = 43.9 fl oz total.
4″ diameter × 6″ tall cylinder:
π × 2² × 6 = 75.4 cu in ÷ 1.805 = 41.8 fl oz net. Add 10% = 46 fl oz total.
3″ diameter sphere:
(4/3) × π × 1.5³ = 14.1 cu in ÷ 1.805 = 7.8 fl oz net. Add 15% = 9 fl oz total.

For irregular shapes, use the water displacement method: fill the mold with water and pour it into a measuring cup. The water volume equals your epoxy volume. Enter this directly using the Custom Volume input in the Mold calculator.

Frequently Asked Questions

How do I convert cubic inches to fluid ounces?

Divide cubic inches by 1.805. This works because 1 US fluid ounce = 1.80469 cubic inches. Example: 72 cu in ÷ 1.805 = 39.9 fl oz. Add your waste buffer on top of this net volume.

What is the volume formula for a cylindrical mold?

Volume = π × r² × height (in cubic inches). For a 4″ diameter, 6″ tall cylinder: radius = 2″, so π × 4 × 6 = 75.4 cu in ÷ 1.805 = 41.8 fl oz. The calculator handles this automatically in the Mold/Casting mode.

How do I measure an irregular mold volume?

Use the water displacement method: fill the mold completely with water, then pour that water into a measuring cup. The reading in fluid ounces is your epoxy volume (net). Add 10–15% as your waste buffer. Enter this total directly using the Custom Volume option.

Does epoxy shrink after curing?

Yes, but only slightly — 1–4% by volume depending on the resin system. This is within your waste buffer range and generally not a concern for most projects. Deep-pour resins tend to shrink more than coating resins. The shrinkage manifests as a slight concave top surface on thick pours.

Epoxy Volume Calculator — Cubic Inches to Fluid Ounces

Cubic Inches to Fluid Ounces — The Key Formula

Volume Formulas for Common Mold Shapes

Real Project Volume Examples

Frequently Asked Questions

Related Calculators & Guides