A graduated cylinder is a tall, narrow container used to measure the volume of liquids. Its slim design gives it better precision than wider containers like beakers or flasks, making it one of the most common measuring tools in science labs, classrooms, and professional settings. It can also measure the volume of small solid objects through a simple water displacement technique.
How a Graduated Cylinder Works
The cylinder’s tall, narrow shape is the key to its accuracy. Because the liquid spreads across a smaller surface area, even a small change in volume produces a noticeable rise in the liquid level. This makes it much easier to get a precise reading compared to a wide beaker, where the same volume of liquid barely changes the height.
Graduated cylinders come in a range of sizes: 10 mL, 25 mL, 50 mL, 100 mL, 500 mL, and 1,000 mL are the most common. Each size has scale markings (called graduations) printed along the side, and the spacing between those markings varies by size. On a 10 mL cylinder, each small line might represent 0.1 mL, while on a 1,000 mL cylinder each line might represent 10 mL. To figure out what each line is worth on any cylinder, subtract two neighboring labeled numbers and divide by the number of small spaces between them.
Some cylinders have markings that increase from bottom to top, designed for measuring as you fill. Others have markings that increase from top to bottom, meant for measuring as you pour liquid out. Dual-scale cylinders include both, so you can read the volume either way.
Reading the Meniscus
When water or most other liquids sit in a graduated cylinder, the surface curves slightly downward in the center, forming a U-shaped dip called the meniscus. You always read the volume at the bottom of that curve, not the edges where the liquid climbs up the glass.
Your eyes need to be level with the liquid surface. If you look down at the cylinder from above, the meniscus will appear higher than it actually is, and you’ll overestimate the volume. Looking up from below causes the opposite error. Set the cylinder on a flat surface, crouch or lift it until your line of sight is perfectly horizontal with the liquid, and read the graduation line that touches the lowest point of the curve.
Measuring Irregular Solids by Water Displacement
Graduated cylinders aren’t just for liquids. If you need to find the volume of a small, oddly shaped object (a rock, a metal part, a marble), you can use a method called water displacement. Pour enough water into the cylinder to fully submerge the object and note the volume. Then gently slide the object in and read the new volume. The difference between the two readings is the volume of the object.
This works for any solid that doesn’t dissolve in water or absorb it. It’s one of the simplest ways to measure volume when the shape of an object makes calculations with a ruler impossible.
Glass vs. Plastic Cylinders
Most graduated cylinders are made from either borosilicate glass or polypropylene plastic, and the choice depends on what you’re measuring.
- Borosilicate glass resists nearly all common chemicals, including acids, bases, and organic solvents like acetone. It also handles heat, cooling, and rapid temperature changes without cracking. The main limitation is that strong alkaline solutions at high temperatures can etch the glass over time.
- Polypropylene plastic is lighter, cheaper, and won’t shatter if dropped. It works well with water-based solutions and mild acids or bases, and holds up in freezers. However, it softens or melts at high temperatures and degrades when exposed to strong organic solvents like chloroform or toluene.
For a typical school lab measuring water or simple solutions, plastic cylinders are practical and safe. For chemistry work involving solvents or heated liquids, glass is the better choice.
Class A vs. Class B Accuracy
Graduated cylinders are manufactured in two accuracy grades. Class A cylinders meet tighter tolerances set by ASTM standards and are marked with the letter “A” on the glass. Class B cylinders share the same basic design but are allowed twice the measurement error of Class A. For routine work like mixing a solution that doesn’t need to be exact, Class B is fine. For anything where precision matters, Class A is worth the higher cost.
You may also notice the markings “TC” (to contain) or “TD” (to deliver) on a cylinder. A TC cylinder is calibrated so the volume markings reflect the liquid inside it. A TD cylinder accounts for the thin film of liquid that clings to the walls after you pour, so the markings reflect the volume that actually comes out. Most graduated cylinders used for pouring are calibrated TD.
How It Compares to Other Lab Glassware
A graduated cylinder sits in the middle of the precision spectrum. Beakers and Erlenmeyer flasks have volume markings, but those are rough estimates, useful for mixing and storing but not for accurate measurement. A graduated cylinder is a significant step up from both.
For the highest precision, though, a volumetric flask is the standard. Volumetric flasks are calibrated to hold one exact volume (50 mL, 100 mL, 250 mL, etc.) and are the go-to tool when you need to prepare a solution at a precise concentration. A graduated cylinder can measure many different volumes across its full range, which makes it more versatile for everyday measuring tasks, but a volumetric flask will be more accurate at its single calibrated volume.
In practice, most lab work involves reaching for a graduated cylinder when you need a reliable volume measurement and a beaker won’t cut it. It’s the workhorse of liquid measurement: accurate enough for the vast majority of tasks, easy to use, and available in a size for nearly any volume you need.