Free ND Filter Calculator

Enter your base exposure (the shutter speed without the filter) and the filter strength — get the exact shutter time for a silky-smooth long exposure.

Exposure

Base shutter speed (seconds)

e.g. 0.5 = 1/2 s · 0.008 = 1/125 s · 4 = 4 s

ND filter

…or enter stops directly

Exposure compensation to apply (stops)

Optional: e.g. +0.33 for the half-stop between 10 and 13 stops.

Result

Shutter time

—

with filter

Effective stops

—

filter + compensation

Base

—

without filter

🌊 Reading: with a on top of a base exposure, you need a shutter speed. Bulb mode + a remote release (or the camera's 2-second timer) is the reliable way to shoot it.

ND filter stops reference

Filter name	Optical density	Stops
ND2	0.3	1
ND4	0.6	2
ND8	0.9	3
ND16	1.2	4
ND32	1.5	5
ND64	1.8	6
ND100	2.0	6.7
ND128	2.1	7
ND256	2.4	8
ND400	2.6	8.7
ND512	2.7	9
ND1000	3.0	10
ND2000	3.3	11
ND4000	3.6	12
ND8000	3.9	13
ND16000	4.2	14
ND32000	4.5	15
ND64000	4.8	16
ND100000	5.0	16.7

Related guides

ND Filter Long Exposure Chart

The full chart: base exposure → shutter time for every filter, printable.

Read →

Depth of Field Calculator

Pair your long exposure with the right aperture for the scene.

Open →

ND filter FAQ

Why does shutter time double with every stop?

Each ND stop halves the light reaching the sensor, so the shutter must stay open twice as long to record the same exposure: 1/60 s at 1 stop becomes 1/30 s, 1/15 s, 1/8 s… With a 10-stop ND1000, a 1/60 s base becomes 1/60 × 2¹⁰ = ~17 s.

What ND strength should I buy first?

ND64 (6 stops) or ND1000 (10 stops) are the two most useful. ND64 suits moving water at mid-day; ND1000 is the classic choice for long exposures of 15–30 s in daylight.

Does stacking two filters add their stops?

Yes — optical densities add, so ND8 (3 stops) + ND64 (6 stops) = 9 stops total. Watch for vignetting and color cast when stacking.