Free Calculator · Published October 2026
Resin Volume Calculator: Cubic Feet and Grain Capacity
Measure the resin bed, or name the grains you need at a real salt dose. You get cubic feet, the capacity that dose delivers, and the nameplate those cubic feet would claim at 15 pounds.
Built by SubcontractorHub — the software plumbing contractors use to quote, finance, and run every job.
Book a DemoResin Volume Calculator for Media, Not the Household
This resin volume calculator does not size a softener from people and hardness. That is the water softener sizing calculator. It also does not price a year of salt. The salt cost calculator stays live for that.
Bed mode measures a tank. Target mode orders resin for a capacity at the dose you will actually run.
Inside diameter of the mineral tank, not the outer jacket.
Depth of resin only. Leave the freeboard out. The empty space is for backwash lift.
📋 Important: All calculator results are ballpark estimates
All calculations are estimates based on historical information and should be verified by the user. This tool is provided as a free service for planning purposes only and is not a substitute for a professional assessment, a supplier quote, or applicable local code requirements. The grain table is a planning curve for standard cation resin.
What the Resin Volume Calculator Returns
A bed is a cylinder of resin, not the tank
Dealers order resin in cubic feet and then pour it into a tank that is taller than the bed. The extra height is freeboard. Backwash needs that room so the beads can lift and the fines can leave. If you type the tank's overall height, the resin volume calculator will tell you to buy media that will not fit once the freeboard is respected.
Measure inside diameter and the depth of resin you intend to install, or the depth you find when you open a tank for a rebed. Gravel underbedding, if the tank uses it, is not resin. Leave it out of the depth. A short-loaded bed is a capacity problem even when the valve screen looks correct. When the beads themselves are finished, the symptoms and the rebed decision are in water softener resin replacement.
Grain capacity depends on the dose
Cubic feet are not grains until you name a salt dose. The planning table on this site rates standard resin near 32,000 grains per cubic foot at about 15 pounds of salt, and fewer grains at a lighter dose. Eight pounds is about 24,000 grains per cubic foot. Six pounds is about 20,000. The nameplate on a tank is the thirsty end of that curve, which is why a 1 cubic foot tank is often sold as 32,000 grains and then programmed at a dose that will not reach 32,000.
| Dose (lb/cu ft) | Grains per cu ft | What the label means |
|---|---|---|
| 4 | 16,000 | Very efficient |
| 6 | 20,000 | Efficient |
| 8 | 24,000 | Balanced |
| 10 | 27,000 | High capacity |
| 12 | 30,000 | Near maximum |
| 15 | 32,000 | Nameplate / maximum |
Pounds of salt for one regeneration are cubic feet times that dose. The full comparison, including grains per pound, is the salt dose calculator. This page only needs the dose so the cubic feet have a grain meaning.
Worked examples
Geometry or a grain target. No household and no bag price.
| Case | Cubic feet | Grains at the dose |
|---|---|---|
| 10 in tank, 30 in bed, 8 lb dose | 1.364 | 32,725 |
| 12 in tank, 36 in bed, 6 lb dose | 2.356 | 47,124 |
| 24,000 grains wanted at 8 lb | 1 | 24,000 |
Where the other tools start
- Hardness, iron, and people decide whether you need a softener at all. That is sizing.
- Days between regenerations need a household. That is the regeneration calculator.
- A known cubic footage and a dose decide salt pounds. That is the salt dose calculator.
- A bag price the customer will actually pay decides the annual bill. That is the salt cost calculator, which stays a separate page.
- Which bag, pellets or crystals or potassium chloride, is a product choice, not a volume.
- Iron above a few ppm fouls resin. Do not rebed a larger tank and call the iron solved.
What to write on the rebed ticket
Inside diameter, resin depth, cubic feet ordered, the dose you will program, and the grains you are willing to claim at that dose. If the poured depth does not match the ticket, the capacity claim is already wrong. A water treatment dealer can keep that note on the same record as the hardness test instead of re-measuring the tank in the driveway a year later. See plans if the office still tracks rebeds in a spreadsheet.
Frequently Asked Questions
How do you calculate softener resin volume?
Treat the resin bed as a cylinder. Cubic feet equal pi times the radius in feet squared times the bed depth in feet. Type the inside diameter of the mineral tank and the depth of the resin, not the height of the empty tank. Freeboard above the bed is supposed to be empty so the resin can lift during backwash. Typing the shell height overstates the resin.
How many grains are in a cubic foot of resin?
On the planning table used across this site, standard resin is about 20,000 grains per cubic foot at 6 pounds of salt, about 24,000 at 8 pounds, and about 32,000 at 15 pounds. The 32,000 figure is the nameplate assumption. A lower dose holds fewer grains. The resin manufacturer's curve overrides the table.
How is this different from the softener sizing calculator?
The sizing calculator starts from hardness, iron, and people and recommends a nameplate. This resin volume calculator starts from a tank you can measure, or from a grain target at a dose you chose, and returns cubic feet. It does not ask how many people live in the house. Use sizing to pick the job. Use this page to order the media or to check a bed you already opened.
How is this different from the salt dose calculator?
The salt dose calculator starts from cubic feet you already know, or from a nameplate divided by 32,000, and returns pounds of salt for one regeneration. This page is how you get the cubic feet when you know the tank or the grains you need. Salt pounds show here only as resin times the dose, so you can see the pair. Annual bags and a bag price stay on the salt cost calculator.
Should I round resin up to a full bag?
The tool shows the calculated cubic feet and the next whole number, because many suppliers sell standard cation resin by the cubic foot. That round-up is a planning convenience, not a claim about your supplier's bag size. If the bag is a half cubic foot or a liter, order in that unit. Do not short a bed to save a partial bag if the grain target was the reason you sized it.
Order the Cubic Feet You Can Explain
Put the bed measurement, the dose, and the grains you promised on the customer record before the resin is poured.
Get a Free DemoAll calculations are estimates based on historical information and should be verified by the user. This tool is provided as a free service for planning purposes only and is not a substitute for a professional assessment, a supplier quote, or applicable local code requirements. Grain figures follow the planning table shared with the salt-dose and salt-cost calculators. This tool does not estimate annual salt cost.