Short answer
Choosing an anchor for a 30-35 ft boat, or a 36-footer in the same range, depends on loaded displacement, windage and how you use the boat. For standard-windage boats in this range, the Knox Fit & Sizing calculator recommends a 9 kg, 13 kg or 18 kg Knox Anchor. Its Cruising profile returns 13 kg or 18 kg, depending on loaded displacement.
Boat length is only the starting point. Two 34-footers can weigh very different amounts and catch very different amounts of wind. That's why you shouldn't choose an anchor for a 30-35 ft boat from length alone. The chart below goes by loaded displacement, which is your boat's weight with fuel, water, gear and stores on board.
At a glance
- An anchor for a 30-35 ft boat is sized from loaded displacement, windage and how you use the boat, not from length alone.
- For standard-windage 30–36 ft boats, the Fit & Sizing calculator returns 9 kg, 13 kg or 18 kg.
- Lunch is the under-25-knot profile; Cruising is under 40 knots.
- Example: a 35 ft boat at 8 tonnes loaded gets 13 kg under Cruising.
- Catamarans, flybridge motor yachts, or boats over 25 tonnes: ask Knox.
- Check that the size you choose will fit your bow before you order.
What size anchor for a 30-35 ft boat? The Knox chart
| Loaded displacement | Lunch profile (under 25 knots) | Cruising profile (under 40 knots) |
|---|---|---|
| Up to 5.5 tonnes | 9 kg | 13 kg |
| Over 5.5 up to 9.5 tonnes | 13 kg | 13 kg |
| Over 9.5 up to 25 tonnes | 18 kg | 18 kg |
| Over 25 tonnes, or a catamaran or flybridge motor yacht | Ask Knox | Ask Knox |
The table uses the Lunch and Cruising profiles on the Knox Fit & Sizing calculator, checked on 13 November 2026. The wind figures are assumptions used by the calculator. Actual holding depends on the seabed, how well the anchor sets and how much scope you use. Allow for gusts, waves and tidal current when choosing an anchorage.
To check the right anchor for a 30-35 ft boat, enter its length overall and loaded displacement in the calculator, then choose the profile that matches how you anchor.
Why loaded displacement and windage matter
Your anchor resists the pull of wind, waves and tidal current through your chain or rope. A higher-sided boat can catch more wind than a lower-profile boat of the same length. Displacement also affects how the boat responds to waves and how loads build on the rode. For the full explanation, see How the Knox Anchor Works.
Before you use the chart, find your boat's loaded displacement. Fuel, water, a tender and cruising kit can all take it above the brochure figure. If you're unsure of the weight, check it before you choose a size.
Should you go one size up?
Sometimes. For fair-weather day anchoring, start with the calculator's Lunch profile. For cruising or overnight anchoring, start with its Cruising profile. If you regularly anchor overnight, use exposed anchorages or live aboard, ask Knox whether the next size would give you useful extra margin. Check that you can still deploy, retrieve and stow the larger anchor safely. Knox FAQ
Before settling in overnight, check that the anchor has set and that you have enough scope and room to swing as the wind and tide change. Anchoring Techniques & Safety
Check it fits your bow
Before you order, check these four things.
- Fluke clearance. Use the full-size Knox template or clearance diagram to check that the fluke clears the hull as the anchor pivots on the roller. Check this especially carefully on a plumb bow.
- Roll-bar arc. Make sure the hoop clears the pulpit and furler drum during deployment and retrieval and when the anchor is stowed.
- Roller width. Knox calls for a channel wide enough for the shank plus 10 mm of clearance.
- Locker fit. If you stow the anchor inside, check that it fits through the opening and that the lid closes with the anchor in place.
If you're unsure, send Knox a photo of your bow roller, your boat model and the anchor size you're considering. Their team can advise on likely fit. Knox Fit & Sizing
When to ask Knox
If your boat is a catamaran, a flybridge motor yacht or another high-windage design, ask Knox for a sizing recommendation. Do the same if your loaded displacement is over 25 tonnes, the upper limit of the calculator. If your bow arrangement is unusual, ask Knox to check the fit of the size you're considering. Contact Knox
FAQ
What size anchor for a 30 ft boat?
For a standard-windage 30 ft monohull weighing up to 5.5 tonnes loaded, the Knox Fit & Sizing calculator returns 9 kg for Lunch and 13 kg for Cruising. Above 5.5 tonnes and up to 9.5 tonnes, it returns 13 kg for both profiles. Above 9.5 tonnes and up to 25 tonnes, it returns 18 kg for both.
What size anchor for a 35 ft boat?
The same chart applies at 35 and 36 ft. For example, the Knox Fit & Sizing calculator recommends a 13 kg Knox Anchor for a standard-windage 35 ft boat with a loaded displacement of 8 tonnes under its Cruising profile.
How much scope should I use?
Knox's typical guidance is about 3:1 in calm conditions, 5:1 for normal anchoring, and 8:1 or more in strong winds, measured from the bow roller to the seabed. Use more scope when you have the room. See Anchoring Techniques & Safety for the full guidance.
Is a heavier anchor always better?
Holding depends on the anchor's shape, how it buries and the seabed it's set in. An oversized anchor can also be harder to deploy, retrieve and stow.
What chain should I use with a Knox Anchor?
Knox specifies Grade 40 or Grade 70 chain. Choose a size suitable for your boat and check that the chain's size and calibration match your windlass gypsy. On an all-chain rode, use a suitably sized nylon snubber to absorb shock loads.
Ready to choose an anchor for a 30-35 ft boat? Read the full Anchor Sizing Guide or shop the Knox Anchor in five sizes from 6.5 kg to 27 kg.
