Free ND Filter Calculator
An ND (neutral density) filter cuts light by a fixed number of stops, allowing longer shutter speeds in bright conditions. 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
Result
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 →Worked example
Say you're shooting a waterfall at 1/125 s and want silky motion blur. Stack an ND1000 (10 stops): 1/125 × 2¹⁰ = 8.2 seconds — set the calculator to ND1000 and it shows exactly that. The pattern to internalize: every 3 stops ≈ 8× the shutter time (ND8 at 1/125 → ~1 s), every 10 stops ≈ 1000×. That's why ND64 (6 stops) is the "moving water at dusk" filter and ND1000 (10 stops) is the "bright midday" filter. Shooting in aperture priority, the camera meters through the filter, so the calculator's real job is telling you before you compose whether the resulting time is 2 s (nice streaks) or 30 s (cotton-candy water).
Related tools & guides
Video ND Filter Calculator
ND stops for the 180° shutter at any frame rate.
Open →ND Filter Long Exposure Chart
The full stops reference table.
Open →Long Exposure Photography Guide
Timing, filters and technique.
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.
ND filter chart: stops to shutter speed
Short answer: each stop doubles the exposure time. A 10 stop filter multiplies a 1/15 s exposure by 1024, which is 68 seconds. A 3 stop filter turns 1/60 s into 1/8 s.
| Strength | Filter name | Light factor | 1 s becomes | 1/15 s becomes |
|---|---|---|---|---|
| 1 stop | ND2 | 2x | 2 s | 1/8 |
| 2 stops | ND4 | 4x | 4 s | 1/4 |
| 3 stops | ND8 | 8x | 8 s | 0.5 s |
| 4 stops | ND16 | 16x | 16 s | 1 s |
| 5 stops | ND32 | 32x | 32 s | 2 s |
| 6 stops | ND64 | 64x | 1 min | 4 s |
| 7 stops | ND128 | 128x | 2 min | 9 s |
| 8 stops | ND256 | 256x | 4 min | 17 s |
| 9 stops | ND512 | 512x | 9 min | 34 s |
| 10 stops | ND1000 | 1024x | 17 min | 1 min |
| 13 stops | ND8000 | 8192x | 137 min | 9 min |
| 15 stops | ND32000 | 32768x | 546 min | 36 min |
Filter names and stops are often confused. ND8 is 3 stops, not 8. ND1000 is 10 stops, and some makers label it ND3.0 or 10 stop. The number after ND is the transmission factor, and stops = log2(factor).
Stacking filters adds stops: a 6 stop and a 3 stop together give 9 stops, a factor of 512. Add the stops, never the filter names. Vignetting and colour cast grow with the stack, so prefer one strong filter.