ND Filter Calculator for Long Exposure

A free ND filter calculator for long-exposure photography. Choose the shutter speed your camera meters without a filter and the neutral density filter you are fitting, and it returns the corrected shutter speed so the photo is exposed the same with the filter on.

How to use an ND filter calculator

Meter without the filter

Find the shutter speed your camera sets before the ND filter goes on.

Pick that base speed

Select it from the list of shutter speeds.

Choose the ND filter

Select your filter and read the corrected shutter speed.

Get the corrected exposure time for any ND filter

Shutter speed without filter

The exposure your camera meters before the ND filter goes on.

ND filter (stops)

The number in brackets is how many stops of light the filter blocks.

Shutter speed with filter

—

Stops of light

—

Light reduction

Each stop doubles the exposure time, so the new shutter speed is the base time multiplied by two to the power of the filter stops. For very long exposures use bulb mode and a remote release, and switch off any in-camera long-exposure noise reduction if you are stacking shots.

Features

Corrected shutter speed Common ND filters Light reduction shown Reads in seconds or minutes

Frequently Asked Questions

How does an ND filter change exposure?

A neutral density filter blocks light by a fixed number of stops. Each stop halves the light, so the shutter must stay open twice as long per stop to keep the same exposure.

What does ND1000 mean?

ND1000 is a 10-stop filter — it cuts the light by about 1000 times. A 1/125 s exposure becomes about 8 seconds with it on, which is why it is popular for smoothing water and clouds.

How do I expose past 30 seconds?

Most cameras only set shutter speeds up to 30 seconds in manual mode. For longer times use bulb mode with a remote release or intervalometer, and time it with the calculator result.

Can I stack ND filters?

Yes — stacking adds their stops together. A 6-stop plus a 3-stop filter gives 9 stops. Just add the stop values and use the total, though stacking can cause vignetting on wide lenses.

💡 Want us to improve this tool just for you?

We can — and it's free! Just send us a quick message with your idea. If you'd like to discuss it in detail, leave your email and we'll get back to you. You can stay anonymous.

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Who is this tool for?

📷 Photographers

Published 18 May 2026 Updated 10 Jun 2026