Lawn & Garden Planning Guide
Proper lawn and garden care starts with accurate measurements and the right amount of materials. Whether you're seeding a new lawn, fertilizing, spreading mulch, or planning irrigation, this calculator helps you determine exactly what you need.
Understanding Lawn Area
Calculating your lawn area is the foundation for all other calculations. Most lawns can be broken into basic shapes (rectangles, circles, triangles) and then added together for complex layouts.
Grass Seed Coverage
- New lawns: Use 8-10 lbs per 1,000 sq ft for full coverage
- Overseeding: Use 3-5 lbs per 1,000 sq ft to fill in thin areas
- Timing: Best results in early fall or spring when soil temps are 50-65°F
Fertilizer Application
Fertilizer rates are measured in pounds of nitrogen (N) per 1,000 square feet. Most lawns benefit from 2-4 applications per year, totaling 2-4 lbs of nitrogen annually.
Mulch Depth Guidelines
- 2 inches: Light coverage for established beds
- 3 inches: Recommended for most garden beds
- 4 inches: Heavy coverage for weed suppression
- 6 inches: Pathways and playground areas
Watering Guidelines
Most lawns need about 1-1.5 inches of water per week, including rainfall. Water deeply 1-2 times per week rather than light daily watering to encourage deep root growth.
Seed Rates, Mulch Coverage, and a Worked Example
The generic "8-10 lbs per 1,000 sq ft" rule only fits a few grasses. Rate depends heavily on seed size: a pound of Kentucky bluegrass holds close to a million tiny seeds, while a pound of tall fescue holds roughly a quarter of that, so fescue needs three to four times the weight to hit the same seed density. Match the rate to your species before you buy.
New-Lawn Seeding Rate by Grass Type
| Grass | Season | New lawn (lbs / 1,000 sq ft) | Best seeding window |
|---|---|---|---|
| Kentucky bluegrass | Cool | 2 - 3 | Late Aug - Oct, or early spring |
| Tall fescue | Cool | 8 - 10 | Late Aug - Oct, or early spring |
| Perennial ryegrass | Cool | 7 - 9 | Late Aug - Oct, or early spring |
| Fine fescue | Cool | 4 - 5 | Late Aug - Oct (shade tolerant) |
| Bermuda (hulled) | Warm | 1 - 2 | Late spring, soil above 65°F |
| Zoysia | Warm | 1 - 2 | Late spring to early summer |
| Buffalo grass | Warm | 2 - 3 | Late spring (USDA zones 3 - 9) |
Cool-season grasses dominate the northern US and transition zone; warm-season grasses suit the South and Southwest. For overseeding an established lawn, use roughly half the new-lawn rate.
Worked Example: a 50 ft × 50 ft Tall Fescue Lawn
Area is 50 × 50 = 2,500 sq ft, which is 2.5 units of 1,000 sq ft. Seeding tall fescue at 9 lbs per 1,000 sq ft gives 2.5 × 9 = 22.5 lbs of seed. For feeding, apply 1 lb of nitrogen per 1,000 sq ft using a 10-10-10 fertilizer: because only 10% of the bag is nitrogen, you need 10 lbs of product per 1,000 sq ft, so 2.5 × 10 = 25 lbs of product. To lay down 1 inch of water, multiply area by 0.623 gallons (the volume of 1 inch of water over 1 sq ft): 2,500 × 0.623 ≈ 1,558 gallons for the week.
Mulch Coverage: Cubic Yards and 2 cu ft Bags
| Bed area | 2 in (yd³ / bags) | 3 in (yd³ / bags) | 4 in (yd³ / bags) |
|---|---|---|---|
| 100 sq ft | 0.62 / 9 | 0.93 / 13 | 1.23 / 17 |
| 250 sq ft | 1.54 / 21 | 2.31 / 32 | 3.09 / 42 |
| 500 sq ft | 3.09 / 42 | 4.63 / 63 | 6.17 / 84 |
| 1,000 sq ft | 6.17 / 84 | 9.26 / 125 | 12.35 / 167 |
Cubic feet = area × (depth in inches ÷ 12); divide by 27 for cubic yards, or by 2 for standard bags. Bag counts are rounded up.
Choosing a Mulch
| Type | Relative cost | Typical lifespan | Best use |
|---|---|---|---|
| Hardwood bark | Low | 1 - 2 yrs | General beds; feeds soil as it rots |
| Cedar | Moderate | 2 - 3 yrs | Rot-resistant, aromatic, foundation beds |
| Pine straw | Low | ~1 season | Slopes and acid-loving plants; needs yearly topping |
| Rubber | Highest | 10+ yrs | Playgrounds and permanent paths; adds no nutrients |
Measurement Mistakes That Blow the Budget
- Forgetting to subtract hardscape. Measure the planted area only. Deduct the house footprint, driveway, patio, and existing beds before ordering seed or fertilizer.
- Mixing up cubic feet and cubic yards. There are 27 cubic feet in a cubic yard. Order 3 cubic feet when you needed 3 cubic yards and you will be nine times short.
- Applying product weight as nitrogen weight. Rates are given in pounds of actual nitrogen. Divide the target N by the first N-P-K number (as a decimal) to get the product weight.