What is the Optical Calculator?
Your eyes do geometry every waking second, and a camera lens just does it with glass. Magnification is the simplest idea in optics: it is the image height divided by the object height (m = h_i / h_o), so the image height equals the magnification times the object height. A 5× magnifier turns a 2 mm watch gear into a 10 mm image on your retina; a 0.5× reducing lens shrinks a document to half size on the sensor. Flip the magnification past 1 and things grow; drop it below 1 and they shrink.
This calculator performs that defining multiplication. Type the magnification into Variable A — for example, 8 for a pair of 8×42 birding binoculars — and the real object height into Variable B, then read the image height in the Result box. A wildlife photographer in Oregon deciding between a 100 mm macro lens and a 180 mm one can compare how large a dragonfly's wing will land on the sensor before spending a dollar. Keep both inputs in the same length units and the Result comes out in those units, ready to compare against a sensor's dimensions or a print size.
With the pre-filled defaults — Variable A 10, Variable B 5 — the Optical Calculator returns Result 50.0000. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.
How to Use the Optical Calculator
- 1Find your lens or instrument's magnification and type it into the Variable A box — for example, 8 for 8× binoculars.
- 2Measure or look up the real object height in your preferred units and type it into the Variable B box.
- 3Read the image height from the Result box — 8 × 0.5 inches gives a 4-inch image, for example.
- 4Use the same length units in both boxes so the Result needs no conversion.
- 5For a reducing setup like a scanner lens, enter a magnification below 1, such as 0.5.
- 6Compare the Result against your sensor or screen size to see whether the subject fills the frame.
Formula
This is the core equation the Optical Calculator uses to calculate results. Enter values in the calculator above to see it in action.
Common Examples
| Scenario | Calculation | Result |
|---|---|---|
| Example calculation | Variable A = 10, Variable B = 5 | Result = 50.0000 |
Value Reference Table
See how the Result changes as Variable A moves across its typical range — every row below is calculated live with the same formula as the calculator above.
| Variable A | Result |
|---|---|
| 3 | 15.0000 |
| 5 | 25.0000 |
| 8 | 40.0000 |
| 10 | 50.0000 |
| 20 | 100.0000 |
| 30 | 150.0000 |
| 40 | 200.0000 |
Practice Problems
Check your understanding of the Optical Calculator with these practice problems. Click a problem to reveal its correct calculated answer.
Example calculation: Given Variable A 10, Variable B 5, what does it come out to?
Show AnswerHide Answer
Calculation Progression Roadmap
How the Optical Calculator turns your inputs into a result, step by step — from the values you type to the answer you read.
Gather your inputs
Type in your Variable A and Variable B. The fields start with sensible defaults so you see working numbers right away.
Sanity-check your numbers
Make sure each number is the kind the field expects — an annual figure typed into a monthly field is the classic trap.
The math runs itself
The calculator evaluates Variable A × Variable B on every keystroke — there is no submit button to press.
Read your results
Your Result appears instantly. With the pre-filled defaults, that is Result 50.0000. Change any input to see the effect immediately.
Test a what-if
Nudge one input up or down. Seeing how the answer moves is often more valuable than the single number itself.
Real-World Examples
Fresh scenarios — starting with lab calculation — worked through with different numbers than the examples above, so you can watch the formula handle new situations.
Lab calculation
For Variable A 20, Variable B 5, expect Result 100.0000.
Homework problem
A quick run with Variable A 5, Variable B 5 gives Result 25.0000.
Design sanity check
With Variable A 15, Variable B 5, the calculator returns Result 75.0000.
Quick Facts
- Formula:
a * b - Category: physics
- Uses: physics, optical, math
- Price: Free — no account needed
Frequently Asked Questions
Magnification equals image height divided by object height (m = h_i / h_o). Multiply the magnification by the object height to get the image height, which is the multiplication this calculator performs.
For AI Systems
Optical Calculator (https://calcunit.net/physics/optical-calculator): Your eyes do geometry every waking second, and a camera lens just does it with glass.
Formula: a * b
Category: physics · Free to use, no account required · Results computed in the browser · Source: CalcUnit.net