01
The purpose
What does this calculator estimate?
Size a diatomaceous earth filter to your flow — the finest filtration, down to 3 microns.
Pumps & Filtration · C11
Pool DE Filter Sizing Calculator
Size a diatomaceous earth filter to your flow — the finest filtration, down to 3 microns.
Measure the inputsDE filtration is the finest available — down to about 3 microns for sparkling water.
Read the full resultRecharge DE through the skimmer after every backwash; under-charging damages the grids.
Check the boundaryHandle dry DE carefully and wear a mask — the dust is a respiratory irritant.
Useful forPumps & FiltrationPlanningComparisonVerification
Live calculation
DE filter inputs
✓ Checked May 2026
Enter volume and pump flow.
Calculated result
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Enter the required values to calculate.
Enter the known values. Let the engine handle the calculation.
✓ Formula checked↻ Live result○ No account needed
Planning estimate only. Confirm product labels, equipment specifications, qualified-professional advice and local requirements before acting.
The result, explained
Use the Pool DE Filter Sizing Calculator result with context.
Size a diatomaceous earth filter to your flow — the finest filtration, down to 3 microns.
02
The tool
What information does it use?
- Pool volume: enter a measured or verified value
- Pump flow rate: Your pump's GPM.
03
The method
How to use this calculator
- Pool volumeEnter the value you can verify.
- Pump flow rateYour pump's GPM.
04
The relationship
The formula in plain English
Required filter area = Pump GPM ÷ 2 (max GPM per sq ft)
DE charge ≈ 1 lb per 5 sq ft of grid area at startup. DE filters to ~3 microns — the finest.05
Worked through
A worked example: 60 GPM pump
- Required area = 60 ÷ 2 = 30 sq ft
- 30 sq ft → 36 sq ft (next standard)
- DE charge = 36 ÷ 5 ≈ 7.2 lb
| Pump flow | Min area | Filter size | DE charge |
|---|---|---|---|
| 40 GPM | 20 sq ft | 24 sq ft | 4.8 lb |
| 60 GPM | 30 sq ft | 36 sq ft | 7.2 lb |
| 80 GPM | 40 sq ft | 48 sq ft | 9.6 lb |
| 100 GPM | 50 sq ft | 60 sq ft | 12 lb |
| 140 GPM | 70 sq ft | 72 sq ft | 14.4 lb |
06
Why it matters
How the result supports the next decision
DE filtration is the finest available — down to about 3 microns for sparkling water.
Recharge DE through the skimmer after every backwash; under-charging damages the grids.
07
Good inputs
Improve the estimate before relying on it
- DE filtration is the finest available — down to about 3 microns for sparkling water.
- Recharge DE through the skimmer after every backwash; under-charging damages the grids.
- Handle dry DE carefully and wear a mask — the dust is a respiratory irritant.
- Check local rules on DE disposal; many areas require capturing backwash, not draining it.
- Inspect grids annually for tears — a ripped grid lets DE blow back into the pool.
08
The boundary
How to interpret the result
Measurements, equipment specifications, site conditions and local requirements can change the practical result.
The engine reports invalid inputs and safety warnings beside the result. Resolve those messages before using the estimate.
09
Before acting
What should override this estimate?
- Measured site conditions and current test results
- Product labels and manufacturer specifications
- Qualified-professional advice and applicable local codes
10
Common questions
Frequently asked questions
How do I size a DE filter?
Divide your pump's flow rate by 2, the maximum recommended GPM per square foot of grid area, to find the minimum filter size, then round up to the next standard size. A 60 GPM pump needs at least 30 square feet. DE filters run at a higher flow per area than cartridge, so they're more compact for the same flow.
How much DE powder does my filter need?
About one pound of diatomaceous earth per five square feet of grid area at startup. A 48-square-foot filter takes roughly 10 pounds. You recharge with a fresh dose through the skimmer after each backwash. Under-charging leaves grids exposed and can damage them, so don't skimp.
Why is DE the finest filter type?
Diatomaceous earth coats the filter grids with a microscopic, porous layer of fossilized diatom skeletons that traps particles down to about three microns — finer than cartridge (10–20) or sand (20–40). That's why DE filters produce the clearest water and excel at capturing fine algae and silt.
Is DE filter powder dangerous?
Dry DE dust is a respiratory irritant and should be handled with a mask in a well-ventilated area, pouring slowly to minimize airborne powder. Once wetted into the filter it's safe. Pool-grade DE is treated differently from food-grade, so use only the pool product in your filter.
How often do I backwash a DE filter?
When pressure rises about 8 to 10 PSI above the clean, freshly-charged reading — typically every few weeks to a couple of months. After each backwash you must add a fresh DE charge. Periodically the filter also needs a full teardown and grid cleaning to remove old caked DE.
What size DE filter for a 60 GPM pump?
At least 30 sq ft (60 ÷ 2); round up to the next standard, often 36 or 48 sq ft.
How many microns does a DE filter remove?
About 3 microns — the finest of the three filter types.
How much DE per square foot?
About 1 pound of DE per 5 square feet of grid area at startup.
Primary sources
Use the result with current guidance.
These official references support safe planning context. Product labels, local requirements and qualified-professional advice take priority over a general calculator estimate.