Plant spacing and seed calculator
How many plants fit in my beds, and how much seed do I need?
Showing for United States
Plants in all your beds
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- Plants in a row
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- Plants in a bed
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- Seeds to sow, or transplants to start, with your germination and spare
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- Packets to buy
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Measure spacings center to center: from the middle of one plant to the middle of the next, and from the middle of one bed or row to the middle of the next.
Plants in a row are rounded down to whole plants; seeds, transplants and packets are rounded up so you do not run short.
Germination, seeds per packet and sowing rates come from your seed packet or supplier. This calculator does not supply them.
Seeds to sow, with your spare
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- Total row length (feet, or meters)
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- Packets to buy
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A sowing rate per foot from a packet is already what to sow, so no germination rate is applied here.
Germination, seeds per packet and sowing rates come from your seed packet or supplier. This calculator does not supply them.
Plants per acre
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- Plants per hectare
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Measure spacings center to center: from the middle of one plant to the middle of the next, and from the middle of one bed or row to the middle of the next.
This is a density: it counts no paths or headlands. Multiply by the area you will actually plant.
Enter your numbers to see the result.
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Get started with TallyTill for freeUse this calculator in an AI chat
You can ask Claude, ChatGPT or another AI app to work this out for you, and this calculator opens right inside the chat. You connect TallyTill to your AI app once. It is free, and there is no account and no sign-in.
AI apps call add-ons like this connectors, apps or MCP servers. They all mean the same thing: a way for the AI to use a tool someone else made.
1. Copy this address
2. Add it to your AI app
Claude (claude.ai and the Claude desktop app)
- Open Customize, then Connectors.
- Press + Add, then Add custom connector.
- Name it TallyTill calculators, paste the address and press Continue.
- Under Authentication choose No sign in, then press Add.
- In a new chat, press + at the bottom left, choose Connectors and switch TallyTill calculators on.
On Claude's free plan you can add one custom connector.
ChatGPT
- In Settings, turn on Developer mode. OpenAI moves this switch from time to time; it is usually with the settings for apps and connectors.
- Add a new connector (ChatGPT may call it an app), paste the address and choose No authentication.
- In a new chat, choose TallyTill from the tools menu, or type @ and pick it.
Not every ChatGPT plan lets you add your own connector. If you cannot find the option, your plan may not include it.
Using another AI app? Look in its settings for MCP, add the address as a remote server, and choose no sign-in.
3. Ask your question
Say "use TallyTill", so the AI uses the calculator instead of doing the sum itself. For example:
"Use TallyTill: How many plants fit in my beds, and how much seed do I need?"
What you will see
- The calculator opens in the chat with the numbers you gave already filled in. Change any number and the answer updates.
- If a number is missing, the box is highlighted, or the AI asks you for it in plain words.
- The answer links back to this page, so you can check the working.
- The first time, your AI app asks if it may use TallyTill. Choose Allow.
The calculators take numbers only. They never ask for your name, your email or a password.
How this is worked out
Plants in a row are the row length divided by the in-row spacing, rounded down to whole plants; a bed holds that times its rows, and your beds hold that times the number of beds. To start enough, the plants are increased by your spare percentage and divided by your germination rate (a germination of 80% means sowing 100 seeds for every 80 plants), then rounded up. Seeds by the foot are the total row length times the seeds per foot from the packet, plus your spare, rounded up. Packets are rounded up. Plants per acre are 43,560 square feet times the rows per bed, divided by the bed spacing times the in-row spacing; per hectare, the same with 10,000 m². The method follows University of Georgia Extension and Penn State Extension.
A worked example
Example numbers only; use your own. Four beds 100 ft long with 2 rows each, plants 18 in apart: 1,200 in ÷ 18 = 66 plants a row, 132 a bed, 528 in all. At 12 in apart that is 800 plants; with a 10% spare and 80% germination, sow 1,100 seeds, or 5 packets of 250. University of Georgia Extension's watermelons on 8 ft beds, 3 ft apart, are 1,815 plants an acre.
Nothing you type here is saved.