THE NUMBERS, EXPLAINED
How to use this calculator.
Compare costs for the same output scope. Quality, timing and capacity must be considered separately.
Start with your inputs
Enter internal fixed cost (£), internal unit cost (£), supplier fixed fee (£), supplier unit cost (£), volume. Keep amounts in the units shown on each field. The example is a starting point, not a recommended value.
| Input | Example value |
|---|---|
| Internal fixed cost (£) | 1000 |
| Internal unit cost (£) | 5 |
| Supplier fixed fee (£) | 0 |
| Supplier unit cost (£) | 10 |
| Volume | 300 |
A worked example
With the example inputs above, in-house cost (£) is 2,500. Change the inputs to explore your own scenario.
| Result | Example answer |
|---|---|
| In-house cost (£) | 2,500 |
| Supplier cost (£) | 3,000 |
| Crossover units | 200 |
How this is calculated
In-house cost (£)
a + b × e
Supplier cost (£)
c + d × e
Crossover units
(c−a)/(b−d). Equal unit costs return no unique crossover.
Symbols and units
- a
- Internal fixed cost (£)
- b
- Internal unit cost (£)
- c
- Supplier fixed fee (£)
- d
- Supplier unit cost (£)
- e
- Volume
Use the units shown. A list keeps the order in which you enter its values. The symbol ^ means “raised to the power of”.
Assumptions and limits
Compare costs for the same output scope. Quality, timing and capacity must be considered separately.
Calculations use the values you enter. Blank or invalid inputs show an error instead of silently substituting zero. Results are displayed to useful precision; calculations retain the underlying numeric precision.
Questions about this tool
What does the result tell me?
In-house cost (£); Supplier cost (£); Crossover units. The result applies to the method and inputs described above. Check the units and assumptions before using it in a decision.
Why might another calculator differ?
Differences in units, rounding, timing or model definitions can produce different answers. Compare the input definitions and the method, rather than only the final number. For this tool: Compare costs for the same output scope. Quality, timing and capacity must be considered separately.
Are my inputs stored or sent to AI?
Calculations on this page happen in your browser. The separate AI question finder sends its submitted conversation to OpenAI; these calculator fields are not sent. Favourites and recent tool names are stored locally. A shared link contains the inputs you choose to include.
Review status
Software example and browser checks are recorded in our quality report. No external expert review is claimed. Created with coding assistance; calculations run as ordinary browser code.
Read the quality report →