Egg case: about 28 days at room temperature, carried by the female (Gould & Deay 1940; UF/IFAS). Nymphs: 41 days at 25 °C, usually 5–6 moults (Peterson et al. 2023). Adults: 100–200 days, 4–8 egg cases of 30–40 eggs (UF/IFAS). Generations: 3–4 a year, up to 6 (UF/IFAS).
German cockroach life cycle
The german cockroach life cycle goes egg case → nymphs → adult, and in a warm kitchen the whole loop takes only about two to three months. At 25 °C (77 °F) the egg case takes about 27 days to hatch and the nymphs about 41 days to become adults (Gould & Deay 1940; Peterson et al. 2023) — about 68 days in total. UF/IFAS describes "the entire life cycle" as about 100 days, and Texas A&M says German cockroaches "can produce a generation in about 100 days".
What makes the life cycle of the german cockroach different from other species is the egg case. The female doesn't drop it: "Eggs are carried in an egg case, or ootheca, by the female until just before hatch occurs" (UF/IFAS), and nymphs often hatch while she is still carrying it. Penn State notes this is why "a greater number of nymphs hatch successfully". Ebeling adds that she forms the first case 11–12 days after becoming an adult (Ross 1929) and may carry it "for as long as a month".
- Egg case: about 28 days at room temperature (Gould & Deay 1940; Penn State), 14 days at 35 °C (Ross 1929).
- Nymphs: usually five or six moults, about 31 days at 30 °C to 87 days at 20 °C (Peterson et al. 2023).
- Adults: 100–200 days (UF/IFAS); each female produces four to eight egg cases (UF/IFAS; Penn State), about one every six weeks at room temperature (Penn State).
The life cycle of a german roach repeats continuously indoors, with no winter break: "German cockroaches breed continuously with many overlapping generations present at any one time" (UF/IFAS).
German cockroach stages from newborn nymph to adult
The german cockroach stages at 24 °C, with the nymph stages split using the 2023 Auburn University measurements:
| Stage | Size | What it looks like | Lasts |
|---|---|---|---|
| Egg case (ootheca) | about 8 × 3 × 2 mm; 30–40 eggs | light brown, purse-shaped; carried by the female | about 28 days at 24 °C |
| Nymph 1 | 3 mm when newly hatched | dark brown to black, two dark stripes, no wings | 7.7 days |
| Nymph 2 | — | dark brown to black, two dark stripes, no wings | 7.4 days |
| Nymph 3 | — | dark brown to black, two dark stripes, no wings | 8.5 days |
| Nymph 4 | — | dark brown to black, two dark stripes, no wings | 9.7 days |
| Last nymph stage(s) (5th, sometimes 6th) | nearly adult size | dark brown to black, two dark stripes, no wings | 17 days |
| Adult | 13–16 mm | light brown, two dark stripes behind the head; wings but doesn't fly | 100–200 days (UF/IFAS) |
Sources: UF/IFAS (egg case size, eggs, colours, adult 10–16 mm), Ebeling (first-stage nymph 3 mm), Peterson et al. 2023 (stage times), Gould & Deay 1940 (egg case time).
German cockroach nymph
A german cockroach nymph is dark brown to black, with dark parallel bands down the shield behind the head and no wings (UF/IFAS). The first-stage nymph is only 3 mm long, with a pale band across the middle of its back that narrows into a stripe as it grows (Ebeling). Field populations are about 80% nymphs (UF/IFAS), so the small dark roaches you see are usually German nymphs, not a second species.
How the German cockroach mother carries her young
The german cockroach egg case is "a tiny, brown, purse-shaped capsule" about 8 mm long, 3 mm high and 2 mm wide (UF/IFAS), with two rows of eggs inside (Penn State). Because the female carries it until hatching, you'll rarely find loose German egg cases; empty, split cases in cracks are a sign nymphs have already hatched. To turn a found case into a hatch window, or compare it with other species' cases, use the roach egg hatch timer.
How many babies does a German cockroach have?
How many eggs does a German cockroach lay? Each case usually holds 30–40 eggs (UF/IFAS), up to 48 (Penn State), and a female produces four to eight cases (UF/IFAS) — usually four or five (Ebeling). That's roughly 120–320 eggs in a lifetime. In Gould and Deay's cultures, an average of 29.9 nymphs hatched per case, and 85% of hatched nymphs reached adulthood in Willis, Riser and Roth's (1958) study (both quoted by Ebeling).
Why German cockroaches multiply so fast
How fast do German cockroaches multiply? Faster than any other common cockroach, for four reasons:
- Big batches: 30–40 eggs per case, against about 16 for American and Oriental cockroaches (UF/IFAS).
- Protected eggs: the female carries the case until hatching, so more eggs survive (Penn State).
- Short development: the "shortest time from hatching until sexual maturity" of the house-infesting species (Penn State).
- No breaks: indoors they breed all year, and a new case starts within a couple of weeks of the last one hatching (Penn State).
The population mode of the calculator turns those numbers into a theoretical maximum: one newly mated female at 24 °C could in theory lead to about 2,561 living cockroaches after 180 days and 1.9 million after a year, if every egg hatched, every nymph survived and nothing ever died early. Real numbers are far lower — about 30 nymphs hatch per case on average, some die at each moult, and many females make only four or five cases — but the University of Kentucky's warning stands: "A single mated female can produce thousands of new cockroaches in less than a year."
German cockroach generations per year
UF/IFAS says there are "generally three to four generations a year, but there may be as many as six under ideal conditions", and Virginia Tech also gives three to four. The shared model agrees: counting from a new egg case to the next generation's first egg case, there's time for about 4.1 german cockroach generations per year at 24 °C and 5.8 at 30 °C.
German cockroach life stages and temperature
The german cockroach life stages all speed up with warmth up to about 30 °C, then slow again. Texas A&M puts the optimum around 80 °F (27 °C). The table shows the life stages of german cockroach by temperature from the shared model:
| Temperature | Egg case | Nymphs: mean (range) | Egg case to adult | Generations a year |
|---|---|---|---|---|
| 20 °C (68 °F) | 28 days * | 87 days (71–119 days) | 115 days | 2.9 |
| 22.5 °C (72.5 °F) | 28 days * | 64 days (54–85 days) | 92 days | 3.5 |
| 25 °C (77 °F) | 27 days | 41 days (37–51 days) | 68 days | 4.6 |
| 27.5 °C (81.5 °F) | 24 days | 36 days (33–50 days) | 60 days | 5.1 |
| 30 °C (86 °F) | 21 days | 31 days (28–49 days) | 52 days | 5.8 |
| 32.5 °C (90.5 °F) | 17 days | 33 days (28–45 days) | 50 days | 6 |
| 35 °C (95 °F) | 14 days | 34 days (28–40 days) | 48 days | 6.2 |
* Egg case not measured below 24.4 °C; the room-temperature figure (about 28 days) is used. Nymph figures are Peterson et al. (2023), who also recorded survival to adulthood of 92% at 20 °C, 94% at 25 °C, 88% at 30 °C and 67% at 35 °C. At 15 °C all nymphs died in their first stage after about 43 days, and the lower development threshold is 14.1 °C — so cool rooms slow German cockroaches dramatically, and the calculator doesn't estimate below 20 °C.
How to tell German cockroaches from other species
The quickest german cockroach identification clue is the two dark stripes running lengthwise on the shield behind the head (University of Kentucky; UF/IFAS). Size helps too: an adult is only about half an inch long.
| Species | Adult size | Key marks | Where you find it | Flies? |
|---|---|---|---|---|
| German (this page) | 13–16 mm | light brown, two dark stripes behind the head | indoors only: kitchens, bathrooms | no |
| Brown-banded | 11–14.5 mm (about ½ in) | two pale bands across the wings; no stripes (University of Kentucky) | warm, dry rooms, high up, furniture | males sometimes |
| Oriental | 22–32 mm (about 1–1¼ in) | shiny black to dark brown, short wings | damp basements, drains | no |
| American | 34–54 mm (1⅜–2⅛ in) | reddish brown, pale band around the shield | basements, sewers, steam tunnels | yes |
| Smokybrown | 25–32 mm (1–1¼ in) | uniform dark mahogany | outdoors: mulch, trees, eaves | yes |
| Florida woods (a "palmetto bug") | 30–40 mm (1⅛–1⁹⁄₁₆ in) | reddish brown to nearly black, short wing pads | outdoors in Florida and the Gulf coast: mulch, logs | no |
| Dubia (feeder) | up to about 45 mm (1¾ in) | dark brown; males winged, females with wing stubs | kept by reptile owners; can't climb smooth plastic | males glide |
| Madagascar hissing (pet) | 5–10 cm (2–4 in) | wingless, glossy brown; males with two humps | kept as pets | no |
Sources: UF/IFAS, University of Kentucky, Penn State and Texas A&M; the feeder and pet rows use the husbandry sources on their own pages. Two outdoor look-alikes, the Asian and field cockroaches, are found outdoors in some southern areas (Texas A&M). If you're unsure, a local extension office can identify a specimen. For all five species' lifespans side by side, see the cockroach lifespan calculator; for the general life cycle and a to-scale nymph identifier, see the cockroach life cycle calculator.
How this calculator works
Both modes use the shared cockroach data model, so the German development times here match the general life cycle and lifespan pages exactly.
- Life cycle timeline: egg case days by straight-line interpolation between about 28 days at 24.4 °C (Gould & Deay 1940) and 14 days at 35 °C (Ross 1929); nymph stages 1–4 and the last stage(s) from the cumulative instar means of Peterson et al. (2023) at 20, 25, 30 and 35 °C. Dates count from the day the egg case formed.
- Population growth estimate (theoretical maximum): each female forms her first egg case 11 days after becoming an adult (Ross 1929), carries it until it hatches, and starts the next 14 days later (Penn State's "within a couple of weeks"), up to 8 cases of 40 eggs (UF/IFAS) within her 210-day adult life (Penn State's 30 weeks). Every egg hatches, every nymph survives, half are female, and males live up to 200 days (UF/IFAS). The count is living nymphs and adults; eggs still in cases are shown separately.
The population figure is a ceiling, not a forecast. It ignores deaths, food limits, crowding and control — real infestations grow far more slowly.
Frequently asked questions
What is the German cockroach life cycle?
Egg case, about five or six nymph stages and the adult. At 25 °C it takes about 68 days from a new egg case to adult (Gould & Deay 1940; Peterson et al. 2023); UF/IFAS gives about 100 days for the whole cycle.
What are the German cockroach stages?
Egg case (ootheca), nymphs (usually 5–6 moults) and adults (UF/IFAS; Peterson et al. 2023).
How many eggs does a German cockroach lay?
30–40 per egg case, up to 48, with four to eight cases per female (UF/IFAS; Penn State) — roughly 120–320 eggs in total.
Does the German cockroach carry its egg case?
Yes, until just before the eggs hatch; nymphs often hatch while she's still carrying it (UF/IFAS).
How fast do German cockroaches multiply?
A generation takes about 100 days (Texas A&M), with three to four generations a year and up to six (UF/IFAS).
How many generations of German cockroaches are there per year?
Three to four, up to six in ideal conditions (UF/IFAS; Virginia Tech).
What does a German cockroach nymph look like?
Dark brown to black with dark stripes and no wings (UF/IFAS); the first stage is 3 mm with a pale band across its back (Ebeling).
How do I identify a German cockroach?
About half an inch long, light brown, with two dark stripes on the shield behind the head (University of Kentucky).
Do German cockroaches breed in winter?
Indoors, yes — they breed continuously (UF/IFAS). At 15 °C, though, nymphs failed to develop (Peterson et al. 2023).
How long does a German cockroach egg case take to hatch?
About 28 days at room temperature (Gould & Deay 1940; Penn State) and 14 days at 35 °C (Ross 1929).
Can one German cockroach start an infestation?
A single mated female can produce thousands of new cockroaches in less than a year (University of Kentucky).
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.