THE NUMBERS, EXPLAINED
How to use this calculator.
Thin-lens geometric approximation. Circle of confusion is your output/viewing assumption.
Start with your inputs
Enter focal length (mm), aperture f-number, focus distance (m), circle of confusion (mm). Keep amounts in the units shown on each field. The example is a starting point, not a recommended value.
| Input | Example value |
|---|---|
| Focal length (mm) | 50 |
| Aperture f-number | 8 |
| Focus distance (m) | 5 |
| Circle of confusion (mm) | 0.03 |
A worked example
With the example inputs above, hyperfocal (m) is 10.466667. Change the inputs to explore your own scenario.
| Result | Example answer |
|---|---|
| Hyperfocal (m) | 10.466667 |
| Near limit (m) | 3.394595 |
| Far limit (m) | 9.486405 |
How this is calculated
Hyperfocal (m)
Let H = a²/(b × d)+a in millimetres. Hyperfocal in metres = H/1000.
Near limit (m)
Let s = 1000c in millimetres. Near limit = H × s/(H+s−a)/1000 metres.
Far limit (m)
When H ≤ s−a, report Infinity. Otherwise far limit = H × s/(H−s+a)/1000 metres.
Symbols and units
- a
- Focal length (mm)
- b
- Aperture f-number
- c
- Focus distance (m)
- d
- Circle of confusion (mm)
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
Thin-lens geometric approximation. Circle of confusion is your output/viewing assumption.
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?
Hyperfocal (m); Near limit (m); Far limit (m). 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: Thin-lens geometric approximation. Circle of confusion is your output/viewing assumption.
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 →