Introduction
A column volume (CV) is the amount of space inside a packed chromatography column. It is the number most protocols use when they say "wash with 5 CV" or "run a 20 CV gradient." This Column Volume Calculator works out that number for you, plus everything that depends on it.
Type in your column's inner diameter and bed height. The tool finds the cross-sectional area, the bed volume, the void volume (the liquid between the beads), and the media volume (the resin itself). You can pick a preset column like a HisTrap, XK, HiLoad, or BPG, or enter your own sizes in mm, cm, inches, or meters.
The calculator also helps you plan the whole run:
- Flow rate and linear velocity: enter one and get the other, plus CV per hour and residence time.
- Process steps: list your equilibration, load, wash, elution, and strip steps in CV and see the buffer volume and time each one needs.
- Sample loading: check your sample as a percent of bed volume and see how much of the binding capacity you use.
- Gradient volume: find total gradient volume and how much buffer A and buffer B to prepare.
- Scale-up: move from a small column to a bigger one while keeping linear velocity the same.
Every answer comes with a step-by-step solution, so you can see the math and check your work. Charts show step volumes and bed makeup. Use it for protein purification, affinity chromatography, ion exchange, size exclusion, or HPLC method planning.
How to use our Column Volume Calculator
Enter your column size, flow settings, process steps, sample details, gradient, and scale-up target. The calculator gives you the bed volume (CV), void volume, media volume, flow rate, linear velocity, residence time, buffer volumes, run time, and scaled-up numbers for a bigger column.
Preset column: Pick a common column from the list to fill in the diameter and bed height for you. Choose "Custom" to type your own. You can still edit any value after picking a preset.
Column inner diameter (ID): Type the inside width of the column tube and pick the unit (mm, cm, m, or in). This sets the cross-sectional area.
Bed height / column length: Type how tall the packed resin bed is and pick the unit. Bed height times area gives the column volume.
Void fraction (ε): Type the share of the bed that is liquid between the beads. Most packed beds are about 0.35.
Display area in: Choose the unit you want the cross-sectional area shown in, such as cm².
Display volumes in: Choose the unit for all volume results, such as µL, mL, L, or m³.
Solve for: Pick "Flow rate" if you know the linear velocity, or "Linear velocity" if you know the flow rate. The other box fills in by itself and locks.
Linear velocity (u): Type the speed of liquid through the bed and pick the unit, like cm/hr. Most resins run at 400 cm/hr or less.
Volumetric flow rate (Q): Type the pump flow rate and pick the unit, like mL/min.
Show Q in / Show velocity in: Choose the units you want the flow rate and velocity results shown in.
Step name: Type a name for each process step, such as Equilibration, Wash, or Elution.
Column volumes (per step): Type how many CV that step needs. The tool shows the buffer volume and the time for each step.
Add step / trash button: Click "Add step" to add a new row (up to 10). Click the trash icon to remove a row.
Sample volume: Type how much sample you will load and pick the unit. This is used to find the percent of bed volume.
Sample concentration: Type how much target is in your sample, like 10 mg/mL. This gives the total mass loaded.
Dynamic binding capacity: Type how much mass the resin can bind per mL of bed. This shows how much of the capacity you use.
Max sample volume (% of BV): Type the load limit you want a warning at. 10% is common for SEC runs.
Show mass in: Choose the unit for mass results, such as µg, mg, g, or kg.
Gradient expressed in: Pick % buffer B, mM, or M for your gradient.
Start and end concentration: Type the gradient's first and last values, like 0 to 100% B.
Buffer B stock concentration: Type the strength of your B buffer. This is only used for mM or M gradients.
Gradient length (column volumes): Type how many CV the gradient runs over. 10 CV or more gives better separation.
Scale by: Pick "Target ID" to scale by a new column width, or "Scale factor" to scale by a set multiple.
Target column inner diameter: Type the width of the bigger or smaller column and pick the unit.
Volume scale factor (×): Type how many times bigger the new column volume should be. Bed height stays the same so velocity does not change.
Calculate and Reset: Results update as you type, but you can click "Calculate" any time. Click "Reset" to go back to the starting values.
What Is a Column Volume?
In chromatography, a column volume (CV) is the amount of liquid it takes to fill the packed bed inside the column one time. It is also called the bed volume (BV). Scientists talk in column volumes instead of milliliters because a method written as "wash with 5 CV" works on a tiny 1 mL lab column and on a huge 20 L factory column.
How Column Volume Is Found
The packed bed is a cylinder, so you use the cylinder volume formula:
- Area = π × (diameter ÷ 2)²
- Bed volume = Area × bed height
A column 1.6 cm wide with a 10 cm bed has an area of about 2.01 cm² and a bed volume of about 20.1 mL. So 1 CV = 20.1 mL.
Void Volume and Media Volume
The bed is not solid. It is full of small beads called resin or media, with liquid in the gaps between them. The void fraction (ε) tells you what part of the bed is liquid. Most packed beds are close to 0.35, meaning about 35% liquid and 65% beads.
- Void volume (V₀) = BV × ε, the liquid space your sample moves through
- Media volume = BV × (1 − ε), the space the beads take up
Flow Rate and Linear Velocity
Two numbers describe how fast liquid moves through a column:
- Flow rate (Q) is volume per time, like mL/min. It is what you set on the pump.
- Linear velocity (u) is speed, like cm/hr. It is flow rate divided by the column area.
Linear velocity matters most because it stays the same when you change column size. Most resins run well between about 100 and 400 cm/hr. Going much faster can squash the beads and raise the pressure. Residence time is how long it takes one column volume to pass through, and longer times usually mean better binding.
Planning a Run in Column Volumes
A normal purification run has steps like equilibration, sample load, wash, elution, strip, and re-equilibration. Each step is listed in CV. Add them all up, multiply by your bed volume, and you know how much buffer to make. Divide by the flow rate and you know how long the run will take.
Sample Load and Binding Capacity
For size exclusion (gel filtration), sample volume should usually stay under about 1–5% of the bed volume, since a big sample spreads the peaks out. For bind-and-elute methods like affinity or ion exchange, volume matters less. What counts is mass. The dynamic binding capacity (DBC) tells how many milligrams of protein each mL of resin can hold. Loading more than the column can hold causes breakthrough, where your product flows out unbound. Most people load to about 80% of capacity to stay safe.
Gradients
A gradient slowly mixes buffer A into buffer B to push bound molecules off the resin. Gradient length is also given in CV. Short gradients under 5 CV often give poor separation. Ten to twenty CV is a common choice for good peak resolution.
Scaling Up and Down
To scale a method, keep the bed height and linear velocity the same and only make the column wider. The scale factor is the ratio of the two cross-sectional areas. Bed volume, flow rate, buffer volume, and sample load all grow by that same factor, while run time stays the same. Going from a 1.6 cm column to a 10 cm column is about a 39× jump. The run still takes the same amount of time, but you need 39 times more buffer.