Choosing the right boilie size is a key decision in carp fishing and can directly affect how many bites you get and the size of carp you catch. In the UK, most anglers rely on boilies between 12mm and 18mm, as this range offers the best balance between attraction and selectivity.
12mm Boilies – Subtle and Highly Effective
12mm boilies are ideal when carp are cautious or feeding lightly. Smaller baits are easier for carp to pick up and are particularly effective in colder conditions or heavily pressured waters.
- Excellent for winter fishing. See our winter carp bait guide.
- Great on venues with high angling pressure.
- Perfect for use with pop-ups and wafters for subtle rigs.
- Ideal for beginners learning bite detection and rig mechanics. Visit our beginner guides.
15mm to 18mm Boilies – The All-Round Choice
15mm and 18mm boilies are the most commonly used sizes across UK carp lakes. They provide enough food signal to hold fish in your swim while still being easy for carp of all sizes to consume.
- Effective all year round in mixed-stock waters.
- Pair well with pellets and particles for balanced baiting strategies.
- Suitable for both short sessions and long campaigns.
20mm+ Boilies – Targeting Bigger Carp
Larger boilies, typically 20mm and above, are often used when specifically targeting bigger carp or trying to avoid nuisance species such as bream, roach, or crayfish.
- Helps deter smaller fish from stripping your bait.
- Best used on waters known for larger carp.
- Works well with boosted attraction using liquids and glugs.
Seasonal Boilie Size Tips
Boilie size should also change with the seasons, as carp feeding behaviour varies throughout the year.
- Winter: Downsize to 10mm–12mm and focus on high-attraction baits. Learn more in our winter carp bait section.
- Summer: Carp feed more confidently, making 15mm–20mm boilies highly effective. See our summer carp bait guide.
Mixing Boilie Sizes for Better Results
Using a mix of boilie sizes in your swim can be extremely effective. Smaller baits encourage confident feeding, while larger baits help keep better fish present for longer. This tactic is commonly combined with advice found in our bait guides.
Final Thoughts
There is no single perfect boilie size for every situation. Start with 12mm to 18mm as a baseline, then adjust based on season, water pressure, and your target fish. Experimenting with different sizes alongside pop-ups, wafters, and complementary feed can significantly improve your carp fishing results.