Test Tube Volume Calculator
A test tube is a cylinder, so its volume is base area times height, but at the bench nobody measures in centimeters of radius. This calculator takes the diameter or radius in millimeters, centimeters or inches, gives the capacity in milliliters, cubic centimeters and fluid ounces, and fills in five standard lab tube sizes at a click. A second tab answers the question you actually ask with a partly filled tube: how much liquid is in it.
Theoretical brim-full volume for a flat-bottomed tube. Real tubes have rounded bottoms and wall thickness, so a maker’s labeled capacity is lower; see the sizes table below.
Quick Answer
A standard 16 × 125 mm test tube holds 25.13 mL to the brim (25.13 cm³, about 0.85 fl oz). Fill the same tube 60 mm deep and the liquid volume is 12.06 mL. Click the 16 × 125 mm preset above, then switch to the Liquid in tube tab, to reproduce both figures.
Key takeaways
- Volume of a cylinder: V = π × r² × h. One cubic centimeter equals exactly one milliliter, so cm³ and mL are interchangeable.
- Calipers read diameter in millimeters: this tool accepts the diameter directly and converts units for you, so no hand conversion is needed.
- The tool computes theoretical brim-full volume for a flat-bottomed tube. Makers label lower nominal capacities because real tubes have rounded bottoms, glass walls and working headspace.
- The Liquid in tube tab computes the volume of a partial fill from the liquid depth, which is what you need when pipetting reagents.
How to use the test tube volume calculator
Two tabs, one formula. Results stay hidden until you calculate.
- Pick the Tube capacity tab (the default) to find how much the tube holds in total.
- Choose radius or diameter: the "Measure by" selector matches whatever you measured. The 16 × 125 mm preset is loaded as an example.
- Enter the diameter and height, pick the unit your measurements are in, and click Calculate capacity. The answer appears in mL, cm³ and fluid ounces with the full step-by-step working.
- Use the presets for the five most common lab sizes: 12 × 75, 13 × 100, 16 × 125, 18 × 150 and 25 × 150 mm. One click fills the fields and runs the calculation.
- Switch to Liquid in tube for a partly filled tube: enter the depth of the liquid column instead of the full height and click Calculate liquid volume.
Bad inputs are rejected plainly: a blank or non-numeric entry ("Please enter a valid number for the radius or diameter."), and zero or negative dimensions ("The radius or diameter must be greater than zero.").
The test tube volume formula
A test tube is a right circular cylinder, so its volume is the area of the circular base times the height. The standard cylinder volume formula, as given in the LibreTexts geometry text, is V = πr²h: square the internal radius, multiply by pi, multiply by the internal height, all in the same unit. For general cylinder volumes beyond lab glassware, our cylinder capacity calculator uses the same math.
r = d ÷ 2 (if you measured the diameter)
1 cm³ = 1 mL and 1 fl oz = 29.5735 mL
Because one cubic centimeter is exactly one milliliter, the cm³ result doubles as the capacity in mL, which is the unit lab work is done in. Fluid ounces are included for kitchen and US customary contexts.
Worked example: the 16 × 125 mm tube
The 16 × 125 mm preset is pre-filled, so clicking Calculate capacity reproduces this exactly.
Liquid-fill version: switch to the Liquid in tube tab with the same tube and a 60 mm liquid depth. The pre-filled depth is 60 mm: V = π × 0.8² × 6 = 12.06 mL. When you are mixing working solutions at a set volume, our chemical dilution calculator and concentration volume calculator take it from there.
Common test tube sizes: brim volume vs labeled capacity
This is where honest calculators differ from naive ones. The tool computes the theoretical brim-full volume of a flat-bottomed tube from its outside dimensions. Manufacturers label a lower nominal capacity, measured with rounded bottoms, real wall thickness and sensible working headroom. Both numbers are "true"; they answer different questions.
| Tube size (OD × length) | Brim volume (this calculator) | Maker nominal capacity | Practical working volume |
|---|---|---|---|
| 12 × 75 mm | 8.48 mL | 5–6 mL | ~4 mL |
| 13 × 100 mm | 13.27 mL | ~10 mL | ~7 mL |
| 16 × 125 mm | 25.13 mL | ~19 mL | ~13 mL |
| 18 × 150 mm | 38.17 mL | ~29 mL | ~20 mL |
| 25 × 150 mm | 73.63 mL | varies by maker | check your supplier |
Nominal figures come from Lab Manager's test tube sizes chart and Simport's technical data sheets (a 12 × 75 mm Cultube is specified at 5 mL; Lab Manager lists the same format at 6 mL nominal). The gap between columns is the point: fill a 16 × 125 mm tube to its geometric brim and you hold 25 mL; the maker calls it a 19 mL tube because the round bottom and safe working level take the rest.
What other test tube calculators miss
Most test tube calculators online accept only the radius in centimeters and return a single number in cubic centimeters. That creates three practical problems. First, people measure tubes with calipers, which read diameter in millimeters, so they must convert twice before they can even use the tool. Second, nobody tells you the result in milliliters or fluid ounces, even though lab work is done in mL. Third, none of them answer the question you actually ask at the bench: how much liquid is in this partly filled tube?
- Radius-only, cm-only inputs: the typical rival tool forces a diameter-to-radius and mm-to-cm hand conversion before you start. The diameter toggle and mm/inch conversion here remove both steps.
- Single-unit output: cm³-only results leave lab workers doing the mL equivalence themselves. This tool shows mL, cm³ and fl oz together.
- No standard sizes: no rival offers one-click presets for the lab sizes people actually buy. The five presets above cover the common culture-tube ladder.
- No partial-fill mode: every rival computes full capacity only. The Liquid in tube tab computes the volume of the liquid column itself.
- No honest boundary: no rival explains why its figure exceeds the maker's labeled capacity. The sizes table above does, with the nominal and working volumes alongside.
Frequently asked questions
Use the cylinder formula V = π × r² × h. Measure the internal radius and internal height in the same unit, square the radius, multiply by pi (3.14159), and multiply by the height. The answer in cubic centimeters equals the answer in milliliters, since 1 cm³ = 1 mL exactly.
Whichever you measured: the calculator has a toggle for both. Calipers usually read the diameter in millimeters, so leave the selector on Diameter and enter the caliper reading directly. The formula needs the radius, which is half the diameter, and the tool halves it for you.
It depends on the size. A 12 × 75 mm tube holds 8.48 mL to the brim but is labeled about 5–6 mL by makers; a 16 × 125 mm tube holds 25.13 mL to the brim against a 19 mL nominal capacity; a 25 × 150 mm tube holds 73.63 mL to the brim. Use the preset buttons above for exact figures.
The calculator computes the theoretical brim-full volume of a flat-bottomed tube from its outside dimensions. Makers label a lower nominal capacity because real tubes have rounded bottoms and glass walls, and the practical working volume leaves headspace below the rim. For a 16 × 125 mm tube that is 25.13 mL brim, 19 mL nominal, and about 13 mL working volume.
It answers the bench question: how much liquid is in this partly filled tube. Enter the depth of the liquid column instead of the full tube height and the tool computes the liquid volume only, which is what you need when pipetting reagents or checking a reaction volume.
Yes. Switch the unit selector to Inches and the tool converts everything to centimeters before applying the formula (1 inch = 2.54 cm). Millimeters divide by 10. You never need to convert by hand.
Yes, a little. The calculator assumes a flat bottom, so its brim volume slightly overstates what a round-bottomed tube holds to the same fill line. The difference is small relative to the total, and the sizes table above shows how maker nominal capacities sit below the geometric figure for exactly this reason.
Yes. It runs entirely in your browser, needs no account, and stores nothing. Copy the result with “Copy my results” or send it to another app with “Share results”.
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References
- Lab Manager. Test Tube Sizes Chart: Dimensions, Volumes, and Material Specs (nominal capacities and practical working volumes for 10 × 75 through 20 × 150 mm culture tubes). Accessed October 24, 2026.
- Simport Scientific. Technical Data Sheet T400-3ADS: 5 mL Culture Tube with Cap (12 × 75 mm disposable culture tube specified at 5 mL nominal capacity). Accessed October 24, 2026.
- Thermo Fisher Scientific. Immuno Tubes and Stoppers, Polystyrene (12 × 75 mm tube listed at 5 mL volume). Accessed October 24, 2026.
- LibreTexts (K-12 Geometry). 9.20: Volume of Cylinders (cylinder volume formula V = πr²h with worked examples). Accessed October 24, 2026.
- Hera Scientific. List of Test Tubes and Bottles Available at MPW (glass tube size-to-capacity listings, e.g. 25 × 100 mm at 25 mL). Accessed October 24, 2026.
- Simport Scientific. Complete Catalogue 2023: Culture Tubes (12 × 75 mm tubes at 5 mL, 13 × 100 mm at 7.2–8 mL, 16 × 100 mm at 12 mL). Accessed October 24, 2026.