Plan your garden or home project in seconds. No signup, no ads tricking you — just fast, accurate answers.
Click any calculator to get started — each has its own dedicated page with tips and guidance.
Figure out exactly how many gallons you need for any room. Accounts for doors, windows, and multiple coats.
Calculate paint →How many bags of soil or mulch do you need? Enter your bed dimensions and get cubic yards, cubic feet, and bag count.
Calculate soil →Estimate what your lawn irrigation costs per year by state. Uses real water rates with the ability to customize for your bill.
Estimate cost →Get a personalized watering interval for 40+ plant species based on pot size and room temperature.
Find my schedule →How many plants fit in your bed? Supports grid, staggered, and square-foot gardening layouts.
Calculate spacing →Diagnose common seed starting problems. Get tips on temperature, light, humidity, and container type for tomatoes, peppers, lettuce, and basil.
Get tips →Calculate how much fertilizer product you need based on your area, NPK ratio, and application rate. Avoid over- or under-fertilizing.
Calculate fertilizer →Find the best companion plants for your main crop. Covers pest management, soil improvement, and space efficiency for 20+ vegetables.
Find companions →Is your plant rootbound? Get a recommended pot size based on species, growth habit, and current container diameter.
Find pot size →Match your houseplants with the right light conditions. Input your window direction, distance, and obstructions for a personalized assessment.
Assess light →Whether you're planning a new vegetable bed, refreshing a room with paint, or trying to figure out how much mulch to order, doing the math by hand is error-prone and slow. Buy too little and you're making extra trips to the store. Buy too much and you're wasting money.
GardenMath calculators are designed to be fast and precise. Enter your measurements, hit calculate, and get an actionable answer in seconds — no account required, no ads in the way.
Each calculator also includes practical tips from gardening experience, so you're not just getting a number — you're getting context that helps you make better decisions.
How many bags of soil do I need for a raised bed? A typical 4×8 foot raised bed filled 12 inches deep needs about 32 cubic feet of soil — roughly 16 bags of 2-cubic-foot soil mix. Use our soil calculator to get an exact count for any dimensions.
How far apart should I plant tomatoes? Most tomato varieties need 24–36 inches between plants in rows spaced 36–48 inches apart. Use our plant spacing calculator to figure out how many plants fit in your specific bed.
What plants grow well together? Classic combinations include tomatoes with basil and marigolds, corn with beans and squash (the Three Sisters), and carrots with onions. Our companion planting guide covers 20+ crops.
How often should I water my pothos? A pothos in a medium pot at room temperature typically needs watering every 7–10 days. Use our houseplant watering guide for a personalized schedule based on your specific conditions.