Plan mouse colony cage demand against NIH Guide Table 3.2 housing density. Enter strains, weight classes, and cage type — get cages needed, facility utilization, alerts, and a growth-rate forecast.
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| Strain | Cage type | Weight class | Animals | Dams | |
|---|---|---|---|---|---|
Default cage floor areas (NIH Guide Table 3.2): standard 75 in², large 140 in², breeding 75 in² (≥51 in² per dam-with-litter).
| Strain | Cage | Weight | Animals | Max / cage | Cages | Utilization |
|---|---|---|---|---|---|---|
| C57BL/6J | Standard | 15 – 25 g | 24 | 6 | 4 | 100% |
| Month | Projected animals | Projected cages |
|---|---|---|
| 1 | 25 | 5 |
| 2 | 26 | 5 |
| 3 | 28 | 5 |
| 4 | 29 | 5 |
| 5 | 31 | 6 |
| 6 | 32 | 6 |
When to use
Do not use for
The NIH Guide measures floor area available to the animal, not the bedding pan footprint. Subtract space taken up by feeders, water bottles, and enrichment huts before entering custom cage areas.
A trio (1 male, 2 females) splits into two breeding units when both females are nursing — and most vivariums require splitting into two cages once the second dam delivers. Enter dams explicitly to avoid undercounting.
A cage of 15-25g mice moves to the >25g class within a few weeks for most strains. Re-run the calculator before the cohort transitions weight classes — especially in aging studies.
Above 85% you have no room to absorb a single incoming shipment, retired-breeder accumulation, or a stuck transfer schedule. The calculator flags this threshold automatically.
Per-cage capacity = floor(cage_area / per_animal_area), with per-animal areas from NIH Guide Table 3.2. Breeding cages use the 51 dam-with-litter minimum and are counted as one cage per dam. Facility utilization = total_cages_needed / facility_capacity 100. Growth forecast = animals (1 + monthly_rate)^month, with cages = ceil(baseline_cages growth_factor).
Last validated 2026-04-06. Calculations are designed for planning and documentation support; verify procurement decisions against manufacturer specifications or institutional SOPs.
ConductScience Cage Census & Capacity Planner (v0.85.0). ConductScience, Inc. 2026. Available at: https://conductscience.com/tools/mouse-cage-census-calculator
National Research Council. Guide for the Care and Use of Laboratory Animals: Eighth Edition. Washington, DC: National Academies Press; 2011. Table 3.2.
Smith AL, Mabus SL, Stockwell JD, Muir C. Effects of housing density and cage floor space on three strains of young adult inbred mice. Comp Med. 2004;54(6):656-663.
The Guide for the Care and Use of Laboratory Animals (8th edition, 2011) Table 3.2 sets the minimum floor area per mouse for grouped housing:
Standard mouse cages used in most North American vivariums (Allentown NextGen 500, Tecniplast GR900) provide 75–140 of usable floor space, which sets the practical animals-per-cage ceiling. The calculator divides cage area by per-animal area, taking the floor as the maximum.
Crowded cages distort more than welfare metrics — they confound experiments. Specific failure modes include:
A planner that enforces NIH Guide minimums up front is the cheapest fix — moving animals after a citation costs days of vivarium staff time and risks losing study power.
Track every cage live with density alerts, QR cage cards, and current animal counts instead of rerunning a spreadsheet before every review.
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