# Reverse Calculation of Joint Cost
This method is used when the problem gives all cost and revenue figures except the allocation method for joint cost. We work backwards from sales to isolate joint cost as a balancing figure.
## The Reverse Calculation Template
For each joint product, build a vertical reconciliation:
```
Joint Cost of A (balancing figure)
(+) Further Process Cost of A
(+) Selling Expenses of A
(+) Profit of A
────────────────────────
= Sales of A
```
Rearranging:
$$\text{Joint Cost of A} = \text{Sales}_A - \text{FPC}_A - \text{Selling Exp}_A - \text{Profit}_A$$
Do the same for Product B (and any other products).
## Adjustment When Balancing Figures Don't Sum to Total Joint Cost
Sometimes the sum of derived joint costs (A + B + ...) does not equal the total joint cost given in the problem. In such cases:
> Distribute the total joint cost in the ratio of the balancing figures of Joint Cost.
This preserves the relative allocation logic implied by profitability data while reconciling to the actual joint cost figure.
## When to Use
- Sales, profits, further processing costs, and selling expenses are all given
- The method of allocation is not specified
- Need to determine implicit joint cost share per product