Mason Bee House Calculator
Tube count, bore size, and mounting height for mason bee houses.
What it does
Mason bees pollinate spring fruit with quiet efficiency, and they ask only for holes: no hive, no honey, no keeper in a veil. A drilled block or bundle of tubes beside bloom can anchor dozens of nesting females.
The tool above takes the target female count. It returns tube count with spares, the bore size and depth, and mounting height in feet or meters.
The default 20 females needs 24 tubes at 5/16 in by 6 in deep, set 3 to 6 ft high facing morning sun. The metric mirror reads 8 mm by 15 cm at 1 to 2 m.
USDA pollinator programs and Xerces Society nesting guides agree on the recipe: right sized bores, shallow roof against rain, morning sun for early flights, mud and unsprayed bloom close by.
Houses need yearly care, not just hanging. Parasites and chalkbrood accumulate in reused tunnels, so swap paper inserts or clean blocks each fall and store cocoons cool until bloom.
How to use
- Type target nesting females.
- Read the tube count first.
- Read hole size beside it.
- Read mounting height last.
- Mount with morning sun and mud nearby.
- Clean or swap tubes each fall.
Formula
- females
- Target nesting females for the season.
- tubes
- Tubes with 20% spare capacity.
- holes
- Bore diameter and tunnel depth.
One tube per female plus 20% spare covers duds, males, and parasite losses across the flight season. USDA pollinator guidance and Xerces nesting habitat notes converge on 5/16 in bores at 6 in depth, mounted low with morning sun and mud access. Counts are planning numbers; local bloom sets the real ceiling.
Worked example
Example: house 20 mason bee females
Imperial defaults: 20 nesting females.
- Goal: 20 nesting female mason bees.
- Tubes: 20 x 1.2 = 24, with spares for mites and duds.
- Holes: 5/16 in diameter, 6 in deep paper or reed tubes.
- Mount: 3 to 6 ft high, facing morning sun.
- Care: swap or clean tubes each fall.
- Tool shows 24 tubes, 5/16 in dia, 6 in deep, 3 to 6 ft high, faces morning sun.
Reference table
| Females | Tubes | Bores |
|---|---|---|
| 20 | 24 | 5/16 in x 6 in |
| 50 | 60 | 5/16 in x 6 in |
| 8 | 10 | 8 mm x 15 cm |
| 100 | 120 | 5/16 in x 6 in |
Limits
- Planning counts, not guaranteed occupancy.
- Bloom and mud limit real nesting.
- One depth fits masons; leafcutters differ.
- Pesticide drift voids the math.
Common mistakes
- Drilling random hole sizes.
- Facing the house into hot afternoon sun.
- Skipping fall cleaning for years.
- Mounting where sprinklers soak tubes.
- Expecting honey from mason bees.
Try it yourself
Quick checks. Answers sit tucked under each question.
House 50 females?
50 x 1.2 = 60 tubes, same 5/16 in by 6 in bores.
House 8 females, metric?
8 x 1.2 = 9.6, rounded to 10 tubes at 8 mm by 15 cm.
Zero females?
Below 1 is not a house: enter 1 to 500 nesting females.
Questions
Which bees use these houses?
Blue orchard and hornfaced mason bees: gentle spring pollinators that nest in ready holes instead of hives.
What hole size?
About 5/16 in (8 mm) wide and 6 in (15 cm) deep. Narrower suits leafcutters, wider invites wasps.
Where do I mount the house?
Three to six feet up, facing east or southeast for morning sun, with a small overhang against rain.
What else do they need?
Mud nearby for walls, early bloom for food, and no pesticides on the forage patch.
Must I clean tubes?
Yes, yearly. Chalkbrood and mites build in dirty tubes, so swap inserts or bake blocks each fall.
Do all visitors nest?
No. Males hatch first and patrol; only established females provision full tubes.