Petri Dish Sizes Explained: Which Diameter Do You Need?
Most people walk into a lab supply order assuming there’s one “standard” petri dish – a single, universal size that works for everything. In reality, petri dish sizes range from compact 35 mm formats used in microscopy to 150 mm large-format plates built for industrial screening. That range matters more than most buyers realize. Choosing the wrong petri dish diameter affects how evenly your media distributes, how much agar you’ll consume per experiment, and ultimately how much your consumables cost over time. This guide breaks down every standard size, explains key petri dish dimensions, includes a quick-reference size chart, and helps you match the right petri dish diameter to your specific application – so you order with confidence the first time.
What Are the Standard Petri Dish Sizes?
Petri dishes are not one-size-fits-all. They come in a defined family of standard diameters, each suited to different workflows, sample volumes, and laboratory environments. The universally recognized workhorse is the 100 mm × 15 mm dish – the most commonly used standard petri dish size worldwide, particularly in research labs across North America. That said, the full-size family spans considerably: 35 mm, 50 mm, 90 mm, 100 mm, and 150 mm diameters are all considered standard petri dish sizes, and each has a well-established role in modern laboratory practice.
It’s important to note that when suppliers list petri dish dimensions, the measurement refers to the outer diameter. Depth, or height, typically falls between 10 mm and 20 mm, depending on the format – standard dishes run 15 mm deep, while deep-well and shallow variants serve more specialized applications.
| Diameter | Depth | Volume Capacity | Surface Area |
| 35 mm | 10 mm | ~2-3 ml | ~9.6 cm² |
| 50 mm | 15 mm | ~10-12 ml | ~28.3 cm² |
| 90 mm | 15 mm | ~20-25 ml | ~63.6 cm² |
| 100 mm | 15 mm | ~25-30 ml | ~78.5 cm² |
| 150 mm | 20 mm | ~50-70 ml | ~176.7 cm² |
Petri Dish Dimensions Explained – Diameter, Depth, and Volume
Understanding petri dish dimensions means considering three measurements: outer diameter, depth, and volume capacity. Each one affects how you work with the dish and how you budget your materials.
Diameter
Diameter is the primary measurement for any petri dish and is always expressed as the outer diameter in millimeters. When someone asks, “What is the diameter of a petri dish?” the most common answer in a general microbiology context is 90-100 mm – these two sizes dominate routine lab use globally. What’s worth knowing for procurement purposes is that the inner diameter is typically 2-3 mm smaller than the stated outer diameter. This distinction matters when fitting lids, using dish inserts, or calculating actual usable surface area for colony counting or cell coverage.
Depth (Height)
The standard depth across most petri dish sizes is 15 mm – deep enough to hold a solid agar layer with headspace for gas exchange, but compact enough to stack efficiently in incubators. Deep-well variants, running 20-25 mm in depth, are used when you need thicker agar pours, extended culture periods without desiccation, or higher-volume liquid applications. At the other end, shallow 10 mm dishes are common in microscopy setups where the working distance between the objective lens and the sample is critical.
Volume Capacity
One of the most practical questions buyers ask is: how many ml are in a standard petri dish? A 100 mm dish holds approximately 25-30 ml of media – enough for a standard pour-plate without risk of overflow. The follow-up question – how many cm² is a petri dish? – matters equally for cell culture and colony counting: a 100 mm dish offers roughly 78.5 cm² of usable surface area. Both figures feed directly into calculating agar batch quantities, per-plate media costs, and the number of dishes a given preparation run will yield. Petri dish volume is not a trivial consideration when you’re running hundreds of plates per week.
Petri Dish Size Chart – Quick Reference Guide
If you need a fast answer before placing an order, use this petri dish size chart as a decision tool. Match your application to the format that fits it, rather than defaulting to whatever size is most familiar.
| Size | Best For | Typical Volume |
| 35 mm | Single-cell imaging, small-scale assays, microscopy | 2-3 ml |
| 50 mm | Small bacterial cultures, classroom experiments | 10-12 ml |
| 90 mm | Microbiology standard, fungal cultures, general lab work | 20-25 ml |
| 100 mm | Most common research standard, bacterial colonies, cell culture | 25-30 ml |
| 150 mm | High-throughput screening, large colony counts, industrial microbiology | 50-70 ml |
These petri dish measurements conform to the formats used by virtually every major lab supplier and are compatible with standard incubator racks, automated colony counters, and imaging platforms. When in doubt, 90-100 mm covers the widest range of protocols.
Which Petri Dish Size Is Right for Your Application?
Matching petri dish size to application is where procurement decisions get practical. Here’s a breakdown of what each format does best – and where it falls short.
35 mm – Small-Scale and Imaging Applications
The 35 mm dish is the format of choice for live-cell microscopy, single-cell assays, and fluorescence imaging workflows. Its small footprint and shallow depth make it compatible with inverted microscope stages, and it’s widely used in cell biology labs and confocal microscopy setups where working with small, defined populations of cells is the goal. For high-magnification imaging specifically, glass-bottom variants of the 35 mm dish are available – these replace the plastic floor with optical-quality glass to eliminate refractive distortion that would otherwise compromise image clarity.
50 mm – Classroom and Small Experiments
The 50 mm dish occupies a practical middle ground – larger than the imaging format but still compact enough to be economical in limited-budget environments. It holds approximately 10-12 ml of agar, which is sufficient for a clean bacterial spread or a straightforward colony isolation. School science programs, university teaching labs, and research groups running preliminary or low-throughput experiments often favor the 50 mm format precisely because smaller petri dish dimensions translate directly into lower media consumption and more efficient bench space usage.
90-100 mm – The Lab Standard
When someone asks what size petri dish is used in microbiology, the answer is 90-100 mm – this is the universal standard. It’s the default format for bacteriology, mycology, food safety testing, pharmaceutical quality control, and the vast majority of academic and industrial research workflows. The 100 mm diameter is slightly more common in US-based research labs. In comparison, the 90 mm format has traditionally been more prevalent in European laboratories – but both accept identical streaking, spreading, and pour-plate protocols without modification. If you’re stocking a general-purpose lab and need a single format that covers the widest range of petri dish uses, 100 mm is the safe choice.
150 mm – Large-Format Applications
The 150 mm dish exists for situations where scale matters more than economy. High colony-count experiments – such as environmental monitoring, large-population mutation screens, or industrial-scale microbiology – benefit from the larger surface area, which reduces crowding and improves counting reliability. Large fungal cultures that spread aggressively also benefit from the additional room. The trade-off is significant: each 150 mm plate requires approximately 50-70 ml of agar, meaning media costs per plate are roughly 2-3× higher than a standard 100 mm dish. For routine work, this format is rarely justified – but in specialized screening or production environments, it’s often indispensable.
Petri Dish Size in Microbiology vs. Cell Culture – Key Differences
One of the most common and costly ordering mistakes in the lab is assuming that petri dish size is the only variable that matters when choosing between dishes. In fact, two dishes with identical petri dish dimensions can be entirely incompatible depending on their intended application, because the surface treatment changes everything.
Petri dishes microbiology are made from untreated polystyrene or glass. Bacteria and fungi grow on the surface of solidified agar, so the dish itself only needs to be inert, sterile, and appropriately sized. Cell culture dishes, by contrast, are TC-treated – tissue culture-treated – meaning the surface has been modified (typically via plasma treatment) to carry a negative charge that promotes mammalian cell adhesion and spreading in liquid media.
A TC-treated 100 mm dish is not a substitute for a standard 100 mm Petri dish microbiology, and vice versa. Using a TC-treated dish for agar-based microbiology work adds unnecessary cost without any benefit. Using an untreated dish for mammalian cell culture means your cells won’t adhere properly, compromising the entire experiment. The quick rule: if you’re growing bacteria or fungi on agar, use a standard petri dish; if you’re growing mammalian cells in liquid media, use a TC-treated cell culture dish – regardless of whether the petri dish diameter looks the same on the spec sheet.
Glass vs. Plastic Petri Dishes – Does Size Affect the Choice?
What to choose: glass or plastic? Material choice and petri dish dimensions intersect in ways that matter for procurement. Plastic polystyrene dishes are available across all standard sizes – 35 mm through 150 mm – are fully disposable, and represent the most common choice for routine lab work precisely because they combine low cost with consistent sterility. Glass dishes, typically borosilicate, are available in the mid-range sizes: 50 mm, 90 mm, and 100 mm. They’re reusable, autoclavable, and better suited to applications involving high temperatures, organic solvents, or other conditions that would degrade plastic over time.
Where petri dish dimensions directly influence the material decision is at the size extremes. Very small 35 mm dishes and very large 150 mm dishes are predominantly available in plastic only – glass options in these sizes are limited and significantly more expensive. If your workflow relies on either of those formats and requires reusability or chemical resistance, it’s worth discussing options with your supplier before committing to a large order.
Choosing the Right Petri Dish Size
The right petri dish size depends entirely on your application, sample volume, and lab workflow – there is no single correct answer for every situation. For most microbiology and general lab use, 90-100 mm is the safe, proven default: it’s compatible with the widest range of protocols, equipment, and reagent volumes. If you’re working at the imaging scale, 35 mm glass-bottom dishes deliver the precision you need. For classrooms or low-throughput work on a budget, 50 mm strikes the right balance. And for large-format colony work or industrial screening, 150 mm is built for exactly that purpose.
Browse our full range of petri dishes by size to find the format that fits your next order – with bulk pricing available across all standard petri dish diameters.
Ready to order? Explore BostonMed Supply’s petri dish catalog for all standard sizes, available in sterile plastic and borosilicate glass formats with fast shipping across the US and internationally.
