- AC input power:
P_in = V × I × PF - DC input power:
P_in = V × I - Mechanical output:
P_out ≈ P_in × η - Impact power:
P_impact = E × (BPM/60) - Duty-adjusted average:
P_avg = P × Duty - Energy:
Wh = P_avg × Hours - Cost:
Cost = kWh × Rate
- Select corded or cordless to match your tool.
- Enter voltage and current from the label or estimate.
- Fill efficiency, hammer rate, and impact energy if known.
- Set duty cycle and total run time for realistic energy.
- Pick material, bit diameter, and depth for power guidance.
- Press calculate to see results above the form.
| Scenario | Type | V | A | PF | η% | BPM | J | Duty% | Min | Input W | Impact W |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Garden anchor holes | Corded | 230 | 2.6 | 0.90 | 70 | 38000 | 1.2 | 55 | 12 | 538 | 760 |
| Brick edging | Cordless | 20 | 28 | — | 68 | 42000 | 1.6 | 60 | 15 | 560 | 1120 |
| Concrete post base | Corded | 230 | 4.2 | 0.92 | 72 | 45000 | 2.4 | 65 | 20 | 889 | 1800 |
Why power planning matters for garden drilling
Garden projects often mix soft soil with hidden hard layers, pavers, brick edging, and small concrete pads. Underpowered tools overheat, stall, and consume more time per hole. This calculator translates your tool’s electrical input into estimated usable output, then adds duty cycle to reflect real drilling behavior. Use it when installing fence posts, raised bed anchors, pergola feet, irrigation stakes, or paving repairs.
Interpreting input power versus impact power
Electrical input power is the energy the drill draws from the outlet or battery during work. Mechanical output is lower because motors and gear trains lose energy as heat. Impact power is estimated from impact energy per blow and the hammer rate, producing a useful comparison when two tools have similar wattage but very different hammer performance. Higher impact power generally improves progress in dense masonry.
Duty cycle, runtime, and realistic energy estimates
Drilling outdoors rarely happens continuously. You reposition, clear dust, check depth, and cool the bit. Duty cycle captures that stop‑start pattern, so average power and total energy better match actual sessions. Multiply duty‑adjusted average input by total hours to estimate watt‑hours and kilowatt‑hours, then apply your electricity rate for cost planning. This is helpful for longer weekend builds and contractor-style schedules.
Task factors: material, bit size, and hole depth
Larger bits remove more material per revolution and increase torque demand. Deeper holes raise friction, heat, and dust loading. Material choice scales the recommendation because brick and stone usually resist drilling more than typical soil layers. The recommended minimum power combines these factors and adds a safety overhead, helping you choose a tool with enough headroom for tough spots, worn bits, or compacted ground conditions.
Using the results to choose safer tool settings
If estimated input power is high, reduce continuous load by lowering pressure, stepping up bit size gradually, and drilling in intervals. For cordless tools, higher current draw can shorten run time and increase battery heating, so consider larger packs or spare batteries. Use the impact power figure to compare hammer efficiency, and keep the recommended minimum power as a planning baseline before purchasing or renting equipment.
FAQs
1) What if my drill label lists watts but not amps?
Enter watts by converting to amps: A ≈ W ÷ (V × PF). If PF is unknown, use 0.9 for a reasonable estimate, then compare results across tools consistently.
2) Should I use the highest hammer rate available?
Not always. Higher hammer rate can help in masonry, but bit quality, pressure, and dust clearing matter. Use the impact power estimate to compare settings and avoid overheating.
3) Why does mechanical output look lower than input?
Motors, electronics, and gears lose energy as heat. Efficiency represents these losses, so output power is a practical estimate of usable work reaching the bit.
4) How do I pick a duty cycle for garden work?
For short holes with frequent repositioning, 40–60% is common. For steady bench drilling, use 70–85%. Lower values improve realism for hot weather and tough material.
5) Is the recommended minimum power a strict requirement?
No. It is a planning heuristic based on bit size, depth, and material. Use it as a headroom target, then confirm with your tool’s specifications and safe operating limits.
6) Can this estimate battery runtime for cordless tools?
It estimates energy use from average input power and time, which helps compare scenarios. True runtime also depends on battery capacity, temperature, and voltage sag under load.