Stages: egg (in an egg case), nymph (several moults) and adult — incomplete metamorphosis, no larva or pupa (Texas A&M). German: about 68 days egg case to adult at 25 °C (Peterson et al. 2023; Gould & Deay 1940). American and smokybrown: about 600 days (UF/IFAS). Smallest: a newly hatched German nymph is about 3 mm (Ebeling).
Cockroach life cycle: egg, nymph, adult
The cockroach life cycle has three stages: egg, nymph and adult. "Cockroaches have a three-stage life cycle," as Texas A&M's extension guide puts it, and every pest species follows the same pattern, just at very different speeds:
- Egg (inside an egg case). Females lay their eggs in a bean- or purse-shaped capsule called an ootheca. Mature females produce 12 to 36 eggs at a time, depending on the species (Texas A&M), and the case protects them from drying out. Some females carry it until just before hatching; others drop or glue it within a day or two.
- Nymph. Nymphs hatch looking like small, wingless adults (University of Kentucky) and grow by moulting — 5–6 times in German cockroaches, 10–13 times in American cockroaches (Peterson et al. 2023; UF/IFAS). They hide in the same cracks and crevices as the adults.
- Adult. After the final moult the roach has full-size wings (short ones in Oriental cockroaches) and can breed. Adults don't moult again.
That is the whole life cycle of a roach. People also search it as cockroach cycle life, cockroach cycle or cycle cockroach; the calculator above dates each part of the cycle for your species and room temperature. At 25 °C, a German cockroach goes from new egg case to adult in about 68 days; an American cockroach takes about 600 days (UF/IFAS).
Eggs get only a short mention here: the egg case is formed, carried or hidden, and hatches after roughly two weeks (German, at 35 °C) to three months (brown-banded, at 22.5 °C), depending on species and warmth (Ebeling). For a hatch window from the day you found an egg case, and what "gestation" means in cockroaches, see how long roach eggs take to hatch.
Cockroach stages and growth
The cockroach stages are the same in every species, but the numbers behind each stage differ enormously. Here are the cockroach life stages of the five common pest species at 24 °C:
| Species | Egg cases per female | What she does with the egg case | Egg case (24 °C) | Moults | Nymphs (24 °C) | Egg to adult |
|---|---|---|---|---|---|---|
| German cockroach | 4–8 egg cases of 30–40 eggs | carried by the female until just before hatching (about 28 days at room temperature) | 28 days | 5–6 | 1.4–2.1 months | 2.4–3 months |
| American cockroach | 9–10 egg cases of 14–16 eggs | dropped within a day of forming (Penn State) | 57 days | 10–13 | 5.3–31.9 months (up to 2.7 years) | 7.1–33.8 months (up to 2.8 years) |
| Oriental cockroach | about 8 egg cases of 16 eggs | carried about 30 hours, then dropped (Penn State) | 67 days | 7–10 | 16.9–17.8 months (up to 1.5 years) | 19.1–20 months (up to 1.7 years) |
| Brown-banded cockroach | about 14 egg cases of 13–18 eggs | carried 24–36 hours, then glued to a surface | 83 days | 6–8 | about 5.3 months | about 8 months |
| Smokybrown cockroach | about 10 egg cases of about 20 eggs | glued to a surface soon after forming | not split | not verified | about 19.7 months (up to 1.6 years) | about 19.7 months (up to 1.6 years) |
| Florida woods cockroach | egg cases of 20–24 eggs | glued to a surface such as a decaying log (UF/IFAS) | 48 days (measured at 30–36 °C) | 6–8 | 3.3–3.9 months | 4.9–5.5 months |
| Dubia roach | litters of 20–40 nymphs | kept inside the female until the nymphs are born | none (live birth) | 6 | 4–6 months | 4–6 months from birth |
| Madagascar hissing cockroach | litters of 15–40 nymphs | kept inside the female until the nymphs emerge | none (live birth) | 6 | 6–7 months | 6–7 months from birth |
Sources: UF/IFAS, Penn State and Ebeling for egg cases and moults; Peterson et al. 2023 (German nymphs), Ebeling (Oriental and brown-banded nymphs), Penn State (American nymphs 160–971 days) and UF/IFAS (smokybrown, about 600 days egg to adult). Smokybrown development isn't split into egg and nymph in the sources we found. Florida woods cockroach: UF/IFAS. The dubia and Madagascar hissing cockroaches don't lay an egg case at all — the female keeps it inside her body and gives birth to live nymphs, so their rows start at birth.
Read the table as life stages of roaches: one stage of protected eggs, a long stretch of nymphs, then adults. The nymph stretch is where roaches stages of life differ most — a few weeks for a German roach in a warm kitchen, a year and a half or more for an Oriental or American cockroach.
Cockroach growth stages: what changes at each moult
The cockroach growth stages (instars) are the steps between moults. With each one the nymph gets bigger and its markings change: German first-stage nymphs are dark grey to black with a pale band across the middle, which narrows into a stripe in later instars (Ebeling); young smokybrown nymphs are black with white bands and white-tipped antennae (Texas A&M); young American nymphs turn from grey-brown to reddish brown after the first few moults (Penn State). In American cockroaches wing pads first show in the third or fourth instar and are about 7 mm long in the last one (Ebeling). These roach growth stages are why one infestation can contain roaches of many sizes at once.
How many times do cockroaches molt?
How many times do cockroaches molt? It varies by species and even by individual: about 5–6 times in German cockroaches (most often six, says UF/IFAS; most had five or six instars in the 2023 Auburn study), 6–8 in brown-banded (Ebeling), 7–10 in Oriental (UF/IFAS; Penn State) and 10–13 in American cockroaches (UF/IFAS). Warmth also changes the count: at 20 °C most German females needed six instars, at 25–30 °C most needed five (Peterson et al. 2023).
Cockroach metamorphosis: why there's no larva or pupa
Cockroach metamorphosis is the "incomplete" or "simple" kind. Butterflies, flies and beetles go egg → larva → pupa → adult, rebuilding their bodies inside the pupa. Cockroaches skip both the larva and the pupa: the nymph that hatches already has the adult's shape, legs and antennae, and "the nymphs resemble adults except that they are smaller and lack wings" (University of Kentucky). Each moult makes it larger, and the last one adds working wings and reproductive organs.
That has a practical consequence. There's no hidden, non-feeding stage: nymphs feed, hide and are exposed to baits in the same places as adults, and the egg case is the only protected stage. A tiny cockroach in your kitchen is not a different insect — it's a cockroach nymph.
Cockroach nymph vs adult
Cockroach nymph vs adult: adults of most species have full wings, nymphs have none (later instars show small wing pads). Nymphs are often darker or patterned differently — German nymphs are dark brown to black with dark stripes, while adults are light brown with two dark stripes behind the head (UF/IFAS). Adult Oriental cockroaches are the exception: their wings stay short, reaching only a little over half the body in males and less in females (Texas A&M), so size and shape matter more than wings for them.
How long does it take for roaches to grow?
How long does it take for roaches to grow from egg case to adult? From about seven weeks to more than a year and a half, depending on species and temperature. Warmth speeds them up — within limits. German nymphs grew fastest around 30 °C and slowed again at 35 °C, and none completed development at 15 °C (Peterson et al. 2023).
| Temperature | German | Brown-banded | Oriental | American |
|---|---|---|---|---|
| 20 °C (68 °F) | 115 days * | 257 days * | 610 days * | egg 57 days; total ~600 days * |
| 22 °C (71.6 °F) | 97 days * | 257 days * | 605 days * | egg 57 days; total ~600 days * |
| 24 °C (75.2 °F) | 78 days * | 244 days * | 596 days * | egg 57 days; total ~600 days * |
| 26 °C (78.8 °F) | 65 days | 205 days | 479 days | egg 50 days; total ~600 days |
| 28 °C (82.4 °F) | 58 days | 161 days | 348 days * | egg 41 days; total ~600 days |
| 30 °C (86 °F) | 52 days | 142 days * | 341 days * | egg 32 days; total ~600 days |
* Outside the measured temperatures for at least one part (egg case or nymphs), so the nearest measured value is used for that part. German egg cases are about 28 days at room temperature (Gould & Deay 1940) and 14 days at 35 °C (Ross 1929); Oriental and brown-banded nymph figures were measured at "room temperature" (placed at 24.4 °C) and at 27.8 and 29.4 °C (Ebeling). American nymphs (160–971 days) weren't measured by temperature, so only their egg case changes. Smokybrown takes about 600 days at any temperature in the data we found.
How fast do cockroaches multiply?
How fast do cockroaches multiply? The German cockroach is the extreme case: a generation in about 100 days (Texas A&M; UF/IFAS), three to four generations a year and up to six (UF/IFAS), with four to eight egg cases of 30–40 eggs per female (UF/IFAS). Bigger species are slow: an Oriental female lays about eight cases of 16 eggs over her life (UF/IFAS), and her young take a year or more to mature. For a dated, temperature-based estimate of a German infestation's theoretical growth, use the population mode of the German cockroach life cycle calculator.
How small can cockroaches be?
How small can cockroaches be? A newly hatched German cockroach is only about 3 mm long — the size of a sesame seed — and an American cockroach hatchling about 3.5 mm (Ebeling). Oriental hatchlings are larger, about 6 mm. The smallest adults among the pest species are brown-banded (11–14.5 mm) and German cockroaches (13–16 mm) (Ebeling; UF/IFAS).
| Species | Newly hatched nymph | Adult | Moults |
|---|---|---|---|
| German cockroach | 3 mm | 13–16 mm (½–⅝ in) | 5–6 (most often 6, UF/IFAS) |
| American cockroach | 3.5 mm | 34–54 mm (1⅜–2⅛ in) | 10–13 (UF/IFAS) |
| Oriental cockroach | 6 mm | 22–32 mm (about 1–1¼ in) | 7–10 (UF/IFAS: 7; Penn State: 7–10) |
| Brown-banded cockroach | not published | 11–14.5 mm (about ½ in) | 6–8 (Ebeling) |
| Smokybrown cockroach | not published | 25–32 mm (1–1¼ in) | not verified |
So the baby cockroach size you're likely to see ranges from a few millimetres for a new hatchling to about the size of an adult German roach for a late American nymph. Brown-banded and smokybrown hatchling sizes weren't in any source we could verify. The size identifier in the calculator shows each species' newly hatched nymph, a half-grown nymph and the adult on one scale with a ruler.
White cockroaches: what freshly molted roaches are
A white cockroach isn't an albino or a separate species. "Completely white nymphs or adults may be seen in a cockroach colony. These are newly molted individuals that have not yet had time to harden their cuticles and to acquire the normal color for the species" (Ebeling). The colour comes back quickly: a newly moulted German adult hardens and darkens "within a few hours" (UF/IFAS), and an American cockroach's new wings take 25–30 minutes to expand, with full colour in 4–5 hours (Gould & Deay 1940, via Ebeling). First-instar American nymphs are also white right after hatching before turning grey-brown (UF/IFAS).
Seeing a white roach means moulting is going on nearby — in other words, a breeding population with nymphs.
How this life cycle calculator works
The calculator uses the shared cockroach data model on this site, so the development times match the lifespan and German pages exactly.
- Life cycle timeline: egg case days, nymph days and egg-to-adult days at your temperature, by straight-line interpolation between measured temperatures (held at the nearest measured value outside them, and flagged). German nymphs are split into stages 1–4 and the last stage(s) using the cumulative instar times of Peterson et al. (2023). Other species show one nymph block, because their instar timings weren't published by temperature. Dates are counted from the day the egg case formed.
- Nymph size identifier: to-scale drawings of each species' newly hatched nymph (Ebeling's lengths), a half-grown nymph (drawn halfway, not a measured size) and the adult (UF/IFAS). For German roaches, "half-grown" means after the third moult, using Peterson et al. (2023); for the others it's a rough halfway estimate and labelled as such.
Sizes and times are averages. Food, humidity and crowding all change how fast nymphs grow, and individuals vary a lot: German nymphs at 20 °C took anywhere from 71 to 119 days (Peterson et al. 2023).
Frequently asked questions
What is the cockroach life cycle?
Egg (in an egg case), nymph and adult — three stages with no larva or pupa (Texas A&M). Nymphs moult several times, growing each time, until the final moult gives adult wings.
What are the cockroach stages?
Egg case, a series of nymph stages (5–6 in German, 10–13 in American cockroaches) and the adult (UF/IFAS; Peterson et al. 2023).
How long does it take for roaches to grow?
About 68 days from egg case to adult for German cockroaches at 25 °C, and about 600 days for American and smokybrown cockroaches (UF/IFAS).
How small can cockroaches be?
A newly hatched German cockroach is about 3 mm long and an American hatchling about 3.5 mm (Ebeling).
How many times do cockroaches molt?
About 5–6 times for German, 6–8 for brown-banded, 7–10 for Oriental and 10–13 for American cockroaches.
Do cockroaches have larvae or pupae?
No. Cockroach metamorphosis is incomplete: nymphs hatch looking like small wingless adults (University of Kentucky).
What is a white cockroach?
A cockroach that has just moulted. Its new skin hardens and darkens within a few hours (UF/IFAS; Ebeling).
What does a cockroach nymph look like?
A small, wingless version of the adult. German nymphs are dark brown to black with dark stripes; young smokybrown nymphs are black with white bands (UF/IFAS; Texas A&M).
How fast do cockroaches multiply?
German cockroaches can produce a generation in about 100 days, with three to four generations a year (Texas A&M; UF/IFAS).
Does temperature change the cockroach life cycle?
Yes. German nymphs took about 87 days at 20 °C but 31 days at 30 °C, and none completed development at 15 °C (Peterson et al. 2023).
How many eggs are in a cockroach egg case?
12 to 36 depending on species (Texas A&M): 30–40 in German, about 16 in Oriental and American, 13–18 in brown-banded (UF/IFAS; Penn State). For hatch times, see the roach egg hatch timer.
What is the difference between a cockroach nymph and an adult?
Adults have wings (short ones in Oriental cockroaches) and can breed; nymphs are smaller, wingless and keep moulting.
Are baby cockroaches a sign of infestation?
Yes. Nymphs and white, freshly moulted roaches mean cockroaches are breeding nearby.
These calculators give estimates from laboratory and extension figures, for education. Real cockroaches vary with strain, food, humidity and insecticide exposure. Cockroach droppings, saliva and shed skins contain allergens that can trigger asthma, especially in children (CDC; Penn State; University of Kentucky) — for health questions, talk to a doctor. For a heavy infestation, contact a licensed pest professional or your local extension service. We give no pesticide advice.