DE Filter Powder Calculator

Q: How much DE do I add after a backwash?

About 80% of the full charge . Backwashing pushes the dirty outer layer of the cake off the grids, but it does not strip the whole coating, so a full recharge packs the tank and drives the pressure up early. On the 48 sq ft example that is 3.84 lb instead of 4.8 lb. Set the calculator to After backwash and it applies the 80% for you; the share is editable if your manual says something different.

Type your DE filter area and get the powder charge in pounds, kilograms and scoops: a full charge on bare grids, or the 80% recharge after a backwash. No signup.

Filter

Filter area

Printed on the filter label and in the manual, e.g. 48 sq ft on a Hayward DE4820.

Unit

sq ft m²

Common sizes

sq ft

Which charge

Charge basis

After backwash Full charge

A backwash strips the dirty surface layer, not the whole coating, so the recharge is 80% of a full charge. Pick Full charge after a teardown, an acid soak, or a grid change, when the filter starts bare.

Rate and scoop

Charge rate

Where the manual and the rule of thumb disagree, the manual wins.

Pounds of DE per 10 sq ft

Editable. The manual figure for your model, divided by (area ÷ 10).

What you are measuring with

Advanced (overrides)

After-backwash share

Share of the full charge you add back after a backwash.

Pounds per scoop

Weigh yours once if it matters. Scoops vary.

Bag size

Used only for the charges-per-bag line.

Add to the filter

—

Full charge: —
Dose now: —

Area → full charge → dose now → scoops

Planning aid, not a service record. Your filter manual states the D.E. charge for your model, and that figure governs.

Export

How this is calculated

One multiplication and one percentage. The filter area sets the full charge; the after-backwash dose is a share of it.

full_charge_lb = (filter_area_sqft / 10) × lb_per_10_sqft
dose_lb        = full_charge_lb × recharge_share    // 80% after a backwash
               = full_charge_lb                     // 100% on a bare filter
dose_kg        = dose_lb × 0.45359237
scoops         = dose_lb / lb_per_scoop
charges_per_bag = floor( bag_lb / dose_lb )

Worked example. A 48 sq ft filter at 1 lb per 10 sq ft is a 4.8 lb full charge. After a backwash you add 80% of that, 3.84 lb, which is 7.7 half-pound coffee-can scoops, near enough seven and a half. A 25 lb bag covers six of those recharges with 1.96 lb left.

1 lb of DE per 10 sq ft of filter area is the published trade rule of thumb (InYo Pools, How Much DE to Add?; Pool Research). It is a convention, not a law of physics: Hayward's Pro-Grid manual states a fixed D.E. capacity per model, and those figures work out at a flat 1.25 lb per 10 sq ft (24 sq ft = 3.0 lb, 36 = 4.5, 48 = 6.0, 60 = 7.5, 72 = 9.0). Both are presets here and the field stays editable, because the number in your own filter manual is the one that governs.

80% after a backwash is the same two sources: backwashing sheds the dirty outer layer of the cake rather than the whole coating, so a full recharge would overfill the tank.

Scoop size is an input, not a constant. The traditional measure, a 1 lb coffee can, holds about half a pound of DE, which is the only scoop figure either source states. Cans and scoops are not standardised, so the second preset is simply a scoop you have put on a set of scales and found to hold a pound. If it matters to you, weigh yours once and type the figure in.

Sources: InYo Pools DIY, How Much DE to Add? (1 lb per 10 sq ft, 80% after backwash, coffee can holds ½ lb); Pool Research, How Much DE to Add To Your Pool Filter (same three figures, plus a per-model table); Hayward ProGrid DE filter product data (D.E. capacity 6 lb on the 48 sq ft DE4820). Pounds convert to kilograms with the exact NIST factor, 1 lb = 0.45359237 kg.

A DE filter does not filter, the powder does. The grids are only fabric; the diatomaceous earth you pour into the skimmer is the actual filter medium, and it has to be replaced every time you wash some of it out. This page answers the one number that job needs: how much DE to add, in pounds, kilograms and scoops, for the filter in front of you.

The rule, and where it comes from

The trade convention is 1 lb of DE per 10 square feet of filter area, so the area printed on the filter label does all the work. A 48 sq ft filter takes 4.8 lb on bare grids, a 60 takes 6 lb, a 72 takes 7.2 lb. That figure is published by InYo Pools and Pool Research among others, and it is a convention rather than a specification.

Manufacturers are entitled to state their own, and some do. Hayward gives the 48 sq ft ProGrid DE4820 a D.E. capacity of 6 lbs, and the rest of that line follows the same flat rate: 3.0 lb at 24 sq ft, 4.5 at 36, 6.0 at 48, 7.5 at 60, 9.0 at 72, which is 1.25 lb per 10 sq ft rather than 1. Both rates are presets above, and the rate field is editable, because when your manual and a rule of thumb disagree the manual wins. That is also why this tool asks for the rate instead of hiding it: a calculator that hard-codes one number is quietly telling you to ignore your own paperwork.

Why a backwash recharge is 80%, not 100%

Backwashing reverses the flow and sheds the dirty outer layer of the cake. It does not strip the grids back to fabric, which is why the same two sources put the recharge at roughly 80% of a full charge rather than a fresh one. On the 48 sq ft filter that is 3.84 lb instead of 4.8 lb. Dose it as if the grids were bare and you overfill the tank: starting pressure sits high, the run to the next backwash is short, and you get to do this again sooner.

The full charge is for a filter that really is starting empty, which in practice means after a teardown, an acid soak, or a grid change. Pick the basis that matches what you just did to the filter and the arithmetic follows.

Scoops are not a unit

A scoop is a volume and DE is sold by weight, so the conversion is a property of the scoop rather than of the powder. The traditional measure, a 1 lb coffee can, holds about half a pound of DE. That is the only scoop figure the published guidance puts a number on, and neither cans nor scoops are standardised, so the second preset is simply a scoop you have weighed at a pound rather than a claim about any particular product. The calculator carries both and lets you type your own. If you count scoops on every visit, weigh one full scoop once and never think about it again.

Where this sits in the visit

Dosing DE is a two-minute step inside a longer job, and the numbers around it live on their own pages. Sizing or replacing the filter is a flow question, not a powder question, and belongs to the pool filter size calculator. Charging for the teardown clean that resets the charge to full is the pool filter cleaning pricing calculator. And the recurring visit this sits inside, the one where the pressure gauge gets read before anyone touches anything, is the weekly pool maintenance checklist. Working out the water volume for the chemistry side of the same visit is the pool volume calculator.

Nothing is saved: no customer record, no filter history, no account. This sizes one charge for one filter. It is a planning aid rather than a service record, and your filter manual states the D.E. charge for your model, which is the figure that governs.

Frequently asked questions

How much DE do I add to my pool filter?

One pound of DE powder for every 10 square feet of filter area, on a filter that is starting bare. A 48 sq ft filter is therefore a 4.8 lb charge, a 60 sq ft filter 6 lb, a 72 sq ft filter 7.2 lb. That is the published trade rule of thumb rather than a specification, and manufacturers can state more: Hayward gives the 48 sq ft ProGrid DE4820 a D.E. capacity of 6 lbs, which works out at 1.25 lb per 10 sq ft. Both rates are presets in the calculator above and the field is editable, because the figure in your own filter manual is the one that governs.

How much DE do I add after a backwash?

About 80% of the full charge. Backwashing pushes the dirty outer layer of the cake off the grids, but it does not strip the whole coating, so a full recharge packs the tank and drives the pressure up early. On the 48 sq ft example that is 3.84 lb instead of 4.8 lb. Set the calculator to After backwash and it applies the 80% for you; the share is editable if your manual says something different.

How many scoops of DE is that?

It depends entirely on the scoop, which is why the calculator asks. The traditional measure, a 1 lb coffee can, holds about half a pound of DE, so a 3.84 lb recharge is roughly seven and a half cans. That is the only scoop figure the published guidance puts a number on, and cans and scoops are not standardised, so the second preset is simply a scoop you have weighed at a pound. If you count scoops rather than weighing, weigh yours once and type the figure in.

What happens if I put in too much DE, or too little?

Both show up as pressure, in opposite directions and on different timescales. Too much packs the tank, so the starting pressure is high and the run to the next backwash is short. Too little leaves grid fabric uncoated, and bare fabric is what blinds with oils and fine debris, which is the damage that ends in a grid change rather than a clean. Neither failure is dramatic on the day, which is exactly why the charge is worth calculating instead of eyeballing.

Does adding DE fix a filter that will not hold pressure?

Not on its own. If the pressure drops away or DE blows back into the pool, the grids or the manifold are the suspects, not the dose, and the answer is a teardown rather than another scoop. What a correct charge does fix is the ordinary drift: a filter that was short-charged after the last backwash reads low, filters poorly, and gets blamed on the pump. Size the filter itself with the pool filter size calculator, and price the teardown clean with the pool filter cleaning pricing calculator.

Sources

How Much DE to Add?: 1 lb of D.E. powder for every 10 square feet of filter area, roughly 80% of that after a backwash, and a 1 lb coffee can holds about ½ lb of DE. InYo Pools (DIY Pool Resources). Retrieved Sep 11, 2026.
How Much DE to Add To Your Pool Filter: one pound of DE per 10 square feet of filter, about 80% of the new-filter amount after a backwash, one scoop or one can equals ½ pound. Pool Research. Retrieved Sep 11, 2026.
ProGrid DE Filter 48 Sq. Ft. (DE4820): stated D.E. capacity 6 lbs. Hayward. Retrieved Sep 11, 2026.
NIST Guide to the SI, Appendix B.8: pound and square-foot conversion factors (1 lb = 0.45359237 kg). NIST. Retrieved Sep 11, 2026.

How we choose and check our formulas