How High Should Grass Be Cut? Mowing Heights That Keep a Lawn Healthy

Cutting height is one of the easiest things to get wrong on a lawn, and one of the easiest to fix. For most UK gardens the right answer sits between 25mm and 40mm, leaning towards the higher end in summer and anywhere the grass is under stress. Cutting shorter than that does not buy you a tidy lawn for longer, it just gives you a thinner one.

The short answer, in millimetres

Mower height dials rarely tell you the actual measurement, so it helps to know roughly what you are aiming for before you start clicking through settings.

• Fine ornamental lawn: 13mm to 25mm. Only realistic if the turf is fescue or bent grass, level, and you mow twice a week.
• Standard family lawn: 25mm to 40mm. This is where most UK back gardens should live.
• Shaded, worn, or drought stressed grass: 40mm to 65mm. Longer leaf keeps a struggling lawn alive.
• Rough grass and orchard areas: 65mm and up, cut occasionally rather than weekly.

If you are unsure, err upwards. A lawn cut slightly too long recovers within one mow. A scalped one can take a whole season to fill back in.

The one third rule matters more than the number

Whatever height you settle on, never take off more than a third of the grass blade in a single pass. Grass feeds itself through its leaves, so removing most of the leaf in one go forces the plant to burn stored energy from the roots. That is what causes the yellow, straw coloured look people get after mowing a lawn that had run away from them.

In practice: if the grass is 90mm tall, do not drop below 60mm on that cut. Wait three or four days, let it recover, then take it down another third. Two or three staged cuts over a fortnight will bring an overgrown lawn back down without any browning at all.

Mowing height through the UK seasons

Spring

Make the first cut of the year high, around 40mm, mainly to tidy and to wake the grass up rather than to shorten it. As growth picks up through April and May you can work gradually down to 25mm to 30mm, dropping one setting at a time rather than in one jump.

Summer

Raise the blade back up to 35mm or 40mm once the weather turns dry. Longer leaf shades the soil surface, keeps the root zone cooler, and slows evaporation. During a proper dry spell go higher still and mow less often. A lawn kept at 50mm through a heatwave will green up again after rain far quicker than one kept short.

Autumn

Come back up to roughly 30mm to 40mm as growth slows. Going into winter with a bit of length helps the lawn cope with wet ground and low light.

Winter

Mostly you should not be mowing at all. If a mild spell leaves the grass shaggy, top it lightly at 40mm on a dry day when the ground is firm enough to walk on without leaving prints.

Grass type changes what is possible

Most UK lawn seed mixes are built around perennial ryegrass and smooth stalked meadow grass. They are tough and hardwearing, which is exactly why they are used in gardens with kids and dogs, but they do not like being cut short. Push a ryegrass lawn down to 15mm and it thins out fast.

The very short, striped, bowling green look comes from fine fescues and bent grasses, which grow low and dense by nature. Those lawns need far more feeding, watering and mowing to stay that way. If your lawn was laid as standard turf or sown from a general purpose mix, 25mm to 40mm is the honest target.

What cutting too short actually costs you

• Shallow roots. Root depth roughly tracks leaf length. Short grass has short roots, so it dries out faster and needs more watering.
• Moss and weeds. Thin turf lets light reach bare soil, which is an open invitation for moss, clover and dandelions.
• Scalped bumps. On uneven ground the high spots get shaved to the soil first, which makes the lawn look worse rather than neater.
• Slower recovery. A short lawn takes far longer to bounce back from a dry spell or a summer of football and paddling pools.

Cutting too long has its own problems

This is not an argument for never mowing. Grass left long gets sappy and soft, falls over instead of standing up, and holds moisture at the base, which encourages disease in a wet autumn. Long clippings also clump on the surface and smother what is underneath. Regular cuts at a sensible height beat occasional dramatic ones.

Getting the height set correctly

• If your mower has individual levers on each wheel, check all four match. One wheel left a setting lower is a common cause of an uneven finish.
• Set the height with the mower on level ground, not on the lawn itself.
• A blunt blade tears rather than cuts, and the damage shows as a grey or brown haze across the tips a day later. Sharpness matters more the shorter you go.
• Cut dry grass where you can. Wet grass compresses under the deck and gives an inconsistent height.

When to raise the blade regardless of the calendar

Go higher during drought, on newly laid turf for the first few cuts, under trees where light is limited, on any area that takes heavy foot traffic, and across bumpy ground you have not levelled yet. In all of those cases the extra leaf length is doing real work.