From electricity cost to a firing fee
An electric bill answers only one part of the pricing question. A firing service also consumes element and relay life, kiln furniture, loading time and studio capacity. This calculator starts with the direct cost of one complete firing and then allocates a share of the resulting price to a customer or group of pieces.
The first subtotal is:
Labour is hours multiplied by the hourly rate. Overhead is the share of rent, insurance, administration or other recurring studio costs assigned to one firing. Use the same currency for every field.
Margin is not the same as markup
A 20% target margin means profit is 20% of the final selling price. It does not mean adding 20% to cost. The calculator therefore uses:
If cost is 80 and the target margin is 20%, the resulting price is 100. Adding 20% to 80 would produce 96 and a realised margin of only 16.7%.
Choose one allocation rule and publish it
A customer who occupies half the usable kiln space is assigned 50% of the full-kiln price. “Usable” matters: posts, shelves, required clearance and the shape of the work reduce nominal chamber volume. Studios commonly choose shelf area, a standard box size, a measured cubic unit, or whole/half/quarter kiln rates. Any can work when it is applied consistently.
The per-piece result divides the allocated fee by the number of pieces in that share. It is useful for internal costing, but a public price per piece can be misleading when a wide platter and a small bead consume very different capacity.
Building the maintenance reserve
Use actual replacement records where available. Add the cost of elements, relays, thermocouples and routine furniture replacement over a practical period, then divide by the number of firings in that period. The reserve is not a prediction that a component will fail after a fixed number of hours; it is a budgeting method.
Review the fee after electricity tariffs, labour rates or kiln performance change. Longer firings and increasing duty cycle may signal worn elements or a heavier schedule, and they change energy cost even when the controller program has the same peak temperature.
What this estimate leaves out
The result does not include tax, card fees, bad debt, refires, special ramps, rush work, ware storage or damage risk unless you place those amounts in overhead. It also does not decide whether unknown clay is safe to fire. A service policy should state accepted materials, maximum temperature, required labels, payment terms and responsibility for damage.