Resin Doming Calculator
A dome is a slice of a sphere, not a cylinder, so multiplying diameter by height overstates it badly. The right formula is πh(3a² + h²)/6, with a as the radius. A 25 mm blank domed 3 mm high holds 750 mm³, which is 0.75 mL; ten of them is 7.5 mL, or 8.3 g at 1.1 g/cm³. A natural dome is roughly 8–12% of the diameter — 2–3 mm on a 25 mm piece — and pushing past that fails, because surface tension is the assumption underneath this calculation. Resin builds its own lens where you place it, and that height is set by viscosity and surface tension rather than by arithmetic. Treat the answer as "how much resin a dome that high contains", then fill to the rim and add drops by eye.
Your numbers
Resin volume
0.75mL
Total
7.5mL
Resin needed
8.3g
Formula
Resin volume = π × Dome height × (3 × (Diameter ÷ 2)² + Dome height²) ÷ 6
Domes run. Without a lip at the edge the resin creeps over the side, sets on the back, and grinding it off takes longer than pouring again — tape the underside or use a bezel with a rim. Low-viscosity resin sold for flood coats will simply spread instead of doming, however little you use. Let the mix stand about half an hour before pouring and most bubbles rise on their own; pass a torch quickly over what is left, because holding it there dents the surface.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Diameter (mm)The longest line across a circle — twice the radius. | 25 | 0 and up |
| Dome height (mm)Height from the surface of the piece to the top of the dome, not its thickness. | 3 | 0 and up |
| CountA plain count of items; it often ends up as the denominator. | 10 | 0 and up |
| Resin density (g/cm³)Grams per cm³ — epoxy sits near 1.1. | 1.1 | 0.8 ~ 1.6 |
Step by step
Quick reference table
Results when only Diameter (mm) changes and everything else stays put.
| Diameter (mm) | Resin volume (mL) | Total (mL) | Resin needed (g) |
|---|---|---|---|
| 12.5 | 0.2 | 1.98 | 2.2 |
| 18.8 | 0.43 | 4.31 | 4.7 |
| 25 | 0.75 | 7.5 | 8.3 |
| 37.5 | 1.67 | 16.71 | 18.4 |
| 50 | 2.96 | 29.59 | 32.6 |
What each result means
| Result | At default values |
|---|---|
| Resin volume (mL)Resin volume to pour — one cm³ is one mL, before what stays in the cup. | 0.75 |
| Total (mL)Every item added together — check whether tax or tip is inside it. | 7.5 |
| Resin needed (g)Resin needed in total, parts A and B together. | 8.3 |
Common mistakes
Domes run. Without a lip at the edge the resin creeps over the side, sets on the back, and grinding it off takes longer than pouring again — tape the underside or use a bezel with a rim. Low-viscosity resin sold for flood coats will simply spread instead of doming, however little you use. Let the mix stand about half an hour before pouring and most bubbles rise on their own; pass a torch quickly over what is left, because holding it there dents the surface.
Glossary
- Diameter
- The longest line across a circle — twice the radius.
- Dome height
- Height from the surface of the piece to the top of the dome, not its thickness.
- Count
- A plain count of items; it often ends up as the denominator.
- Resin density
- Grams per cm³ — epoxy sits near 1.1.
- Resin volume
- Resin volume to pour — one cm³ is one mL, before what stays in the cup.
- Total
- Every item added together — check whether tax or tip is inside it.
- Resin needed
- Resin needed in total, parts A and B together.
Frequently asked questions
Q. How is Resin Doming Calculator calculated?
Resin volume = π × Dome height × (3 × (Diameter ÷ 2)² + Dome height²) ÷ 6 — A dome is a slice of a sphere, not a cylinder, so multiplying diameter by height overstates it badly. The right formula is πh(3a² + h²)/6, with a as the radius. A 25 mm blank domed 3 mm high holds 750 mm³, which is 0.75 mL; ten of them is 7.5 mL, or 8.3 g at 1.1 g/cm³. A natural dome is roughly 8–12% of the diameter — 2–3 mm on a 25 mm piece — and pushing past that fails, because surface tension is the assumption underneath this calculation. Resin builds its own lens where you place it, and that height is set by viscosity and surface tension rather than by arithmetic. Treat the answer as "how much resin a dome that high contains", then fill to the rim and add drops by eye.
Q. Can you walk through an example?
With Diameter 25mm, Dome height 3mm, Count 10, Resin density 1.1g/cm³, the answer is Resin volume 0.75mL.
Q. What do I need to enter?
Enter Diameter, Dome height, Count, Resin density. The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only Diameter (mm) moves the answer to Diameter (mm) 12.5 → Resin volume (mL) 0.2 and Diameter (mm) 50 → Resin volume (mL) 2.96. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
Domes run. Without a lip at the edge the resin creeps over the side, sets on the back, and grinding it off takes longer than pouring again — tape the underside or use a bezel with a rim. Low-viscosity resin sold for flood coats will simply spread instead of doming, however little you use. Let the mix stand about half an hour before pouring and most bubbles rise on their own; pass a torch quickly over what is left, because holding it there dents the surface.
Related calculators
Materials differ in density and absorption. If your label states a figure, use it — the defaults here are only common values.