NPK Calculator | N-P-K Fertilizer Rate & Blend Planner

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N-P-K Fertilizer Calculator (Composition % → Application Rate / Blends)

Q: "Can I blend two fertilizers?"

"Yes. Add two or more rows and choose the 'No shortage' mode. The calculator finds a combination that meets targets without shortages."

Q: "My units are different."

"Use the unit toggle to switch between kg/ha and lb/acre."

Q: "What if a nutrient is missing?"

"Shortages are highlighted in red and the tool suggests possible adjustments."

Calculate fertilizer rate from label composition (e.g., 10-10-10) and hit your target N-P-K quickly.

Supports blending, loss rate, unit conversion, and optional cost estimates.

Try a quick example

One tap to prefill a typical scenario and see how the output looks.

通用设置

Units and notation apply to both targets and fertilizer labels.

单位

P/K notation

损耗率

Currency

舍入

Target nutrients

Enter target based on soil tests or regional recommendations.

计算模式

No shortage (≥ target), minimize total cost

Default. Uses costs when available, otherwise minimizes total rate.

Match N only

Meet N target; P/K are shown as surplus/shortage.

Match P only

Meet P target; N/K are shown as surplus/shortage.

Match K only

Meet K target; N/P are shown as surplus/shortage.

Fertilizers (blendable)

Add 2-3 fertilizers for a typical blend. 10-10-10 format is accepted.

名称	N-P-K %	Price / unit	Max rate	Must use	操作

高级设置

Optional upper limits help reflect regulations or salt constraints. 'Must use' adds a tiny minimum allocation.

使用方法（3 步）

Enter your target N/P/K rates.
Add fertilizers (labels like 10-10-10 are accepted).
Choose the calculation mode and read the results.

How the calculation works

Single fertilizer

Let fN be the nutrient fraction (N% / 100) and L the loss rate.

Required amount A for target Tn is:

A = Tn / ((1 - L) × fN)

Blended fertilizers

We solve for non-negative rates that satisfy nutrient targets while minimizing cost.

If costs are missing, we minimize total application rate.

minimize Σ(cost_i × x_i) s.t. Σ(x_i × fN_i) × (1 - L) ≥ Tn Σ(x_i × fP_i) × (1 - L) ≥ Tp Σ(x_i × fK_i) × (1 - L) ≥ Tk

常见问题

Can I blend two fertilizers?

Yes. Add two or more rows and choose the 'No shortage' mode. The calculator finds a combination that meets targets without shortages.

My units are different.

Use the unit toggle to switch between kg/ha and lb/acre.

What if a nutrient is missing?

Shortages are highlighted in red and the tool suggests possible adjustments.