Power Drill Battery Runtime Calculator
Knowing roughly how long a battery will last helps you decide whether to buy a spare pack before starting a big job, rather than finding out halfway through a task. Enter your battery specs and typical power draw below for an estimate.
Estimate your drill battery runtime
Enter your battery specs and typical power draw to estimate continuous runtime.
A 2Ah, 18V battery stores 36Wh. At 150W continuous power draw, that gives you:
14 minutes
This is continuous full-load drilling time. In real-world use with trigger pulls, bit changes and breaks, a single battery typically lasts a full day of intermittent DIY work.
Recommended products
A few well-reviewed cordless drills and batteries.
- 18V Cordless
- 2 Years
£89.99
Pros
- 18V battery works across the Bosch Home & Garden range
- Hammer action copes with masonry walls
- Ships with 2 batteries and a carrying case
Cons
- Bulkier carrying case than a bare-unit drill
- 18V Cordless
- 3 Years
£129.99
Pros
- Brushless motor for longer runtime and less wear
- Compact XR design reaches tight spots
- Supplied with a 5.0Ah battery, charger and case
Cons
- Higher price than hobbyist drills
£34.99
Pros
- No battery to charge or replace
- Variable speed with lock-on switch and hammer action for masonry
- Affordable entry point for occasional DIY
Cons
- Mains lead limits reach outdoors
- Heavier than most cordless models
Frequently asked questions
Is this the runtime I should expect in normal use?
This figure is continuous drilling time at your chosen power draw. In real use, you're pulling the trigger in short bursts with breaks in between, so a single battery typically lasts a full day of intermittent DIY work rather than running down in a few minutes.
How do I find the voltage and capacity of my battery?
Both figures are printed directly on the battery pack itself, usually as something like '18V 2.0Ah', and you can also find them in the product listing or manual for your drill.
What's a typical power draw for a cordless drill?
Light drilling into wood or drywall might draw around 100-150W, while heavier drilling into masonry, driving large screws, or using a hammer action can push power draw well above 300W.
Does a higher-capacity battery always mean a heavier drill?
Generally yes, since more cells are needed to store more energy, so a higher-capacity battery adds weight and bulk in exchange for longer runtime between charges.
How this calculator works
The calculator uses a straightforward formula to estimate runtime: Runtime (hours) = Battery Capacity (Wh) / Power Draw (Watts). Battery capacity is measured in Watt-hours (Wh), representing the total energy stored. The power draw, or ‘motor wattage’, is the amount of electricity the drill motor consumes during operation – this varies significantly depending on the drill’s intended use and the material being drilled. We've factored in a safety margin to account for inefficiencies and variations in real-world conditions.
The calculator defaults to an assumed power draw based on common drilling applications (light wood, plasterboard, metal), but you can adjust this value if you know your drill’s specific wattage or have data from the manufacturer. Remember that higher power draws will significantly reduce runtime – a hammer drill, for instance, will consume considerably more energy than a standard drill.
Battery Capacity and Power Draw Comparison - UK Drill Models
| Drill Model | Battery Capacity (Wh) | Motor Wattage (Watts) | Estimated Runtime (Light Wood - 2Ah Battery) |
|---|---|---|---|
| Ryobi One+ 18V Cordless Drill Kit | 18.0 | 360 | 45 minutes |
| Bosch GSR 18V-35 Quick) | 18.0 | 750 | 20 minutes |
| DeWalt DCD796H 18V Brushless Drill/Driver | 18.0 | 760 | 30 minutes |
| Worx Cordless Drill BGD550LI | 5.0 | 350 | 60 minutes |
Worked example: Estimating Runtime on a Plasterboard Project
Let’s say you're using a Ryobi One+ 18V Cordless Drill Kit (£99 at Amazon UK) to drill ten holes into standard UK plasterboard (approximately 12.5mm thick) for hanging shelves. The drill motor wattage is rated at 360 Watts, and the battery capacity is 18Wh. Using our calculator, we get a runtime of approximately 45 minutes – a reasonable estimate considering you’ll need to switch batteries periodically.
However, if you were drilling into metal studs or using a hammer drill function (which significantly increases power draw), the runtime would be considerably shorter. It's always best to overestimate your needs and have a spare battery pack on hand, especially for larger projects; a replacement 18V Ryobi One+ battery costs around £35 at Amazon UK.
More questions answered
What units are used in the calculator?
The calculator uses Watt-hours (Wh) for battery capacity and Watts (W) for motor wattage. These are standard units for measuring electrical power, allowing you to accurately estimate runtime based on your drill’s specifications.
How accurate is this calculator?
This calculator provides an *estimate* – actual runtime will vary depending on factors like the material being drilled, drilling speed, ambient temperature, and battery age. It's a valuable tool for planning but shouldn't be treated as a definitive prediction.
What if my drill doesn’t have a specified wattage?
If you can't find an exact wattage figure, use the power draw rating of a similar drill from the same manufacturer. Alternatively, you could contact the manufacturer for guidance - many offer technical specifications online.
Does this calculator account for battery degradation?
No, it doesn’t directly account for battery degradation. As batteries age, their capacity decreases, leading to shorter runtimes. Factor in a 10-20% reduction in runtime for older batteries.
How does the hammering function affect runtime?
Using the hammer drill function significantly increases motor wattage due to the impact force. This will dramatically reduce your battery’s runtime – typically by 50-70%, depending on the drill and material being drilled.
What's the difference between Wh and Ah?
Watt-hours (Wh) measure energy, while Ampere-hours (Ah) measure current. Battery capacity is often quoted in Ah, but to calculate runtime accurately, you need to know the battery’s voltage (V) as well – Wh = Voltage x Ah.
I'm drilling into brick - will this calculator still be accurate?
Not particularly! Brick requires a much higher power draw than wood or plasterboard. You should manually increase the motor wattage in the calculator to reflect the increased load, perhaps doubling it as a starting point.
Can I use this calculator for other tools?
Yes, you can adapt the calculator for other cordless tools like circular saws and sanders, but ensure you accurately determine the tool's power draw (wattage) before entering the values.
What if I’m unsure about my drill’s specifications?
Consult the manufacturer's website or product manual. Many manufacturers provide detailed technical specifications online, including motor wattage and battery capacity information. Amazon UK listings often have customer reviews with helpful details too.
Should I always buy a larger battery for longer runtime?
While a larger battery will increase runtime, it also increases the weight and cost of your kit. Consider your project needs carefully – a smaller battery might be sufficient for lighter tasks, while a larger capacity battery is preferable for demanding projects or frequent use.