What is the one-third rule?

Never remove more than one-third of the grass blade length in a single mow. Cutting too short stresses the grass and promotes weeds and moss.

Should I mow higher in shade?

Yes. Raise the mower by 10-15 mm in shaded areas. Longer blades capture more light and produce healthier grass in low-light conditions.

What height should I mow before winter?

Raise to 40-50 mm for the last few cuts of the year. This protects the crown of the grass plant through winter.

Does mowing height affect moss?

Yes. Mowing too short weakens grass and encourages moss. Maintaining the correct height for your grass type helps grass outcompete moss.

What is the one-third rule for mowing?

Never cut more than one-third of the grass blade length at once. Cutting too short stresses the grass and weakens root growth, making the lawn vulnerable to weeds.

GardenCalcs

Lawn Mowing Height Calculator — Ideal Cut Height

Find the ideal mowing height for your grass type and season.

Grass Type

Season

Usage Level

How We Calculate This

Mowing height recommendations are based on grass type and season, following RHS and amenity grassland guidelines.

General purpose: 25-40 mm. Fine/ornamental: 10-20 mm. Hard-wearing: 30-50 mm. Wildflower: 50-100 mm.

Heights are adjusted seasonally — lower in summer when growth is active, higher in spring/autumn transitions and winter.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates based on standard gardening guidelines. Results may vary with soil conditions, climate, and plant varieties.