Lens Calculator
Calculate image distance and magnification from the thin lens equation.
Check Lens Calculator
Formula result
Check before you use it
What the numbers show
The answer tells you where the image forms and whether it is enlarged, reduced, upright, or inverted under the ideal lens model.
Use lens calculator for image-formation problems, magnification checks, and basic optics labs.
A negative image distance typically indicates a virtual image under the common sign convention.
Copy-ready formula handoff
Use this after solving the live calculator result, then paste the answer into a lab note, homework check, or engineering review.
1/f = 1/do + 1/di, m = -di / do
- Focal length: Lens focal length using the thin-lens sign convention.
- Object distance: Distance from the lens to the object.
- Image distance: Distance from the lens to the image.
- Magnification: Image size relative to object size.
- The calculator uses the thin-lens approximation.
- Distances should follow one consistent sign convention.
- Mixing sign conventions for object distance, image distance, and focal length in the same calculation.
- Treating a negative image distance as an error instead of checking whether it represents a virtual image.
Lens Calculator result: [paste the solved value from the calculator above]. Formula used: 1/f = 1/do + 1/di, m = -di / do Inputs checked: Focal length, Object distance, Image distance, Magnification. Assumptions: The calculator uses the thin-lens approximation. Distances should follow one consistent sign convention. Worked example: Convex lens with f = 0.10 m and object distance 0.25 m. Enter f = 0.10 m and do = 0.25 m. Solve the thin-lens equation for di. Use m = -di/do to determine image size and orientation. Next check: Mixing sign conventions for object distance, image distance, and focal length in the same calculation.
Equation context
Built for image-formation problems, magnification checks, and basic optics labs. This page pairs the live calculator with the governing formula, variable glossary, and a worked example so the result is easier to trust and reuse.
Quick entry points
Use the calculator to verify arithmetic after you set up the formula yourself.
Change one input at a time to see which variable is driving the result.
Review the formula notes before using the answer in a lab or design check.
Variables to track
Lens focal length using the thin-lens sign convention. Unit: m.
Distance from the lens to the object. Unit: m.
Distance from the lens to the image. Unit: m.
Image size relative to object size. Unit: -.
Formula method and unit assumptions
Formula and example
Worked example
Convex lens with f = 0.10 m and object distance 0.25 m
- 1Enter f = 0.10 m and do = 0.25 m.
- 2Solve the thin-lens equation for di.
- 3Use m = -di/do to determine image size and orientation.
Lens problems become easier when you separate image location from magnification instead of trying to reason about both at once.
Assumptions
Common mistakes
Related formula checks
Equation context and next checks
Formula and variable setup for Lens Calculator
Calculate image distance and magnification from the thin lens equation. The page is designed to help you move from the known values to the correct formula without rebuilding the derivation every time.
For lens calculator, the safest workflow is to confirm the unit system first, then map each symbol to the physical quantity in your problem statement before solving.
- f: Focal length (m) - Lens focal length using the thin-lens sign convention.
- do: Object distance (m) - Distance from the lens to the object.
- di: Image distance (m) - Distance from the lens to the image.
- m: Magnification (-) - Image size relative to object size.
How to read the result
The answer tells you where the image forms and whether it is enlarged, reduced, upright, or inverted under the ideal lens model.
This tool is especially useful for image-formation problems, magnification checks, and basic optics labs. The output becomes more trustworthy when you compare nearby cases instead of relying on one single run.
- Image distance
- Magnification
- Real vs virtual image hint
Assumptions and limits
The calculator applies the standard textbook relation for this topic, which makes it a strong first-pass answer but not always a full real-world model.
Before you use the result in a lab, design review, or report, check whether the simplified assumptions still match the physical system you care about.
- The calculator uses the thin-lens approximation.
- Distances should follow one consistent sign convention.
- Real lenses can introduce aberrations not captured by the ideal relation.
Quick glossary
Lens focal length using the thin-lens sign convention.
Distance from the lens to the object.
Distance from the lens to the image.
A simplified physics model that omits secondary effects so the first-order relationship is easier to inspect.
Formula checks before using the result
Formula questions
Checks before using the result
When should I use the lens calculator?
Use lens calculator for image-formation problems, magnification checks, and basic optics labs, especially when the governing formula is already known and the main need is a fast, transparent calculation.
What is the main thing the lens calculator tells me?
The answer tells you where the image forms and whether it is enlarged, reduced, upright, or inverted under the ideal lens model.
What can make the lens calculator answer inaccurate?
The answer is exact for the formula and assumptions on the page, but it can drift when the real system violates those assumptions. Common limits include The calculator uses the thin-lens approximation. Distances should follow one consistent sign convention. Real lenses can introduce aberrations not captured by the ideal relation.
Formula references and related examples
Formula Basis