Mirror Sizing Calculator
Mirror dimensions for wall or vanity from room proportions.
About this calculator
This calculator sizes a mirror and estimates the silvering chemistry needed to produce it, supporting rectangular, oval/elliptical, and circular shapes (for circles, the width input doubles as diameter). Area comes from straightforward geometry — including a Ramanujan approximation for ellipse perimeter, used only when a bevel width is specified, since bevel processing cost scales with edge length, not area. Glass weight uses the standard soda-lime density of 2,500 kg/m³. The silvering figures model the classic wet-chemistry mirror process: a thin sensitizing tin layer, then chemical silver deposition, then a protective copper layer, then paint backing.
The calculator assumes about 0.9 grams of metallic silver per square meter of mirror (delivered via roughly 1.5 grams of silver nitrate solution per square meter, since only part of the AgNO3's mass is silver), 0.4 grams of copper per square meter for the protective backing layer, and 200 ml of backing paint per square meter across two coats. These are typical values for float-glass silvering, not measurements from a specific vendor's process — actual silver deposition rates vary with bath chemistry, temperature, and glass surface prep, so use the totals as a planning estimate for batch chemical ordering rather than an exact recipe. The cost estimate scales glass cost with thickness, adds a flat per-square-meter silvering charge for chemistry and labor, and adds bevel processing cost by linear meter of beveled edge when a bevel width greater than zero is entered.
Inputs
Results
Mirror area (m²)
0.54
How to Use This Calculator
- Enter Width (or diameter for circular mirrors) and Height in mm.
- Enter Glass Thickness in mm and select the Shape: rectangle, oval/ellipse, or circle.
- Enter Number of Mirrors to produce and any Bevel Width in mm.
- Review Mirror Area in m² and ft², Glass Weight per mirror, and Total Silver required.
- Check Silvering chemicals (silver nitrate, copper) and Backing Paint quantities for studio batch planning.
How the result changes with Width / diameter (mm)
| Width / diameter (mm) | Mirror area (m²) |
|---|---|
| 300 | 0.27 |
| 450 | 0.41 |
| 900 | 0.81 |
| 1,500 | 1.35 |
What each input means
- Width / diameter (mm)
- Mirror width (or diameter for circular mirrors).
- Height (mm)
- Mirror height (ignored for circular shape).
- Glass thickness (mm)
- Mirror glass substrate thickness. Common: 3, 4, 5, 6 mm.
- Number of mirrors
- How many identical mirrors to produce.
- Shape
- 0 = Rectangle, 1 = Oval/Ellipse, 2 = Circle.
- Bevel width (mm)
- Width of decorative beveled edge. 0 = no bevel.
What each result means
- Mirror area (m²)
- Surface area of one mirror.
- Mirror area (ft²)
- Surface area of one mirror in square feet.
- Weight per mirror (kg)
- Weight of one mirror including glass substrate.
- Silver needed (g)
- Total metallic silver for all mirrors (~0.9 g/m²).
- Silver nitrate (g)
- Silver nitrate solution needed for silvering.
- Copper backing (g)
- Copper for protective backing layer.
- Backing paint (ml)
- Paint for backing protection (2 coats).
- Est. material cost ($)
- Approximate material cost including glass, silvering, and bevel work.
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersWidth / diameter (mm) = 600, Height (mm) = 900, Glass thickness (mm) = 4, Number of mirrors = 1 = 6 input(s) provided
- Calculate Mirror areaMirror area0.54 = 0.54
- Calculate Mirror areaMirror area = areaSqM * 10.76395.81 = 5.81
- Calculate Weight per mirrorWeight per mirror = areaSqM * (thicknessMm / 1000) * 25005.4 = 5.4
Engine last updated . Checked against 2 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Why does selecting a circular shape only ask for width, not height?
For circular mirrors, the calculator reuses the width input as the diameter and computes area as pi times radius squared, so the height field has no effect on a circle's area calculation. Height only matters for the rectangle and oval/ellipse shapes, where it's a genuinely independent dimension.
Why does the calculator need 1.5 grams of silver nitrate to deposit 0.9 grams of metallic silver?
Silver nitrate (AgNO3) is a compound where silver is only part of the total molecular mass — the rest is nitrogen and oxygen that don't end up in the finished mirror coating. The calculator's ratio accounts for that, so the silver nitrate figure is always larger than the metallic silver figure for the same mirror area.
Why does bevel width affect cost through perimeter rather than area?
A beveled edge is a strip of ground and polished glass running along the mirror's outer boundary, so the amount of bevel work scales with how much edge there is to grind, not how much surface area the mirror covers. That's why the calculator computes perimeter (using the Ramanujan approximation for ovals) specifically when a nonzero bevel width is entered, and prices bevel work per linear meter rather than per square meter.
Why might my actual silvering chemical usage differ from this calculator's totals?
The silver, copper, and paint coverage rates used here are typical figures for the wet-chemistry silvering process, not measurements tied to a specific bath formulation or vendor's chemistry. Actual deposition rates shift with bath concentration, solution temperature, and how well the glass surface is cleaned and sensitized beforehand, so treat the totals as a batch-ordering estimate rather than an exact recipe.
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