Plant care calculator

NPK 10-26-26 High-PK Fertilizer Calculator

Use the NPK calculator pre-loaded with the low-nitrogen 10-26-26 high-PK ratio.

Quick Answer

NPK 10-26-26 is a low-nitrogen high-PK fertilizer analysis containing 10% Nitrogen (N), 26% Phosphate (P₂O₅), and 26% Potash (K₂O). In elemental terms, it provides 10% N, 11.3464% P, and 21.5852% K. Use the calculator above to calculate exact product mass and elemental PPM delivery for your target volume.

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Enter your details

Enter your details below to generate a custom recommendation.

Fertilizer

Enter the N-P-K numbers from your fertilizer label.

Sets a recommended default strength and shows a feeding-frequency tip for this plant type. Does not alter the underlying calculation — you can override the strength above at any time.

Calculation Method

Enter the fertilizer amount stated on the product label.

Selecting a plant type below will suggest a default here — you can still choose any strength manually.

Target nitrogen concentration in mg/L (ppm).

Water Volume

Enter the amount of water you are mixing.

The Problem

Most NPK calculators online are built for field-scale agriculture — hectares, acres, kg/ha, Urea/DAP/MOP. Home growers with a bottle of liquid feed and a windowsill of houseplants need a calculator scaled to a watering can or a single pot, not a wheat field.

When to Use This Tool

Use this calculator when you want to measure fertilizer according to a manufacturer's label rate, intentionally dilute that rate (e.g. half or quarter strength for sensitive plants), or calculate the fertilizer amount needed to reach a specific nitrogen concentration (ppm).

Who is this for?

  • Houseplant growers
  • Container gardeners
  • Small-scale home growers

Guaranteed Analysis vs. Elemental Breakdown

Fertilizer packaging labels list nutrient content as nitrogen (N), phosphate (P₂O₅), and potash (K₂O). The actual elemental nutrient availability in solution is derived using standard conversion factors (P = P₂O₅ × 0.4364, K = K₂O × 0.8302).

Nutrient Element Guaranteed Label Analysis Elemental Equivalent
Total Nitrogen (N) 10% 10% N
Available Phosphate (P₂O₅) → Elemental P 26% P₂O₅ 11.3464% P
Soluble Potash (K₂O) → Elemental K 26% K₂O 21.5852% K

Formula & Worked Calculation Example

Elemental P % = P₂O₅ % × 0.4364 = 26% × 0.4364 = 11.3464% P

Elemental K % = K₂O % × 0.8302 = 26% × 0.8302 = 21.5852% K

Product Mass (g) = (Target N ppm × Volume L) / (N % × 10)

Elemental P ppm = Target N ppm × (Elemental P % / N %)

Elemental K ppm = Target N ppm × (Elemental K % / N %)

Benchmark Worked Example (100 ppm N in 10 Liters)

  • Required Mass: (100 ppm × 10 L) / (10% × 10) = 10.000 g product
  • Delivered N Concentration: 100.00 ppm N
  • Delivered Elemental P Concentration: 100 ppm × (11.3464% / 10%) = 113.46 ppm P
  • Delivered Elemental K Concentration: 100 ppm × (21.5852% / 10%) = 215.85 ppm K

Calculated Nutrient Delivery at Target Nitrogen Concentrations

Mathematical dilution scenarios based on guaranteed analysis. This table illustrates solution delivery and is not a universal feeding recommendation.

Target N (ppm) Product Mass (g / 10 L) Delivered N (ppm) Delivered Elemental P (ppm) Delivered Elemental K (ppm)
50 ppm 5.000 g 50.00 ppm 56.73 ppm 107.93 ppm
100 ppm 10.000 g 100.00 ppm 113.46 ppm 215.85 ppm
150 ppm 15.000 g 150.00 ppm 170.20 ppm 323.78 ppm
200 ppm 20.000 g 200.00 ppm 226.93 ppm 431.70 ppm

Sibling NPK Grade Comparison

Comparing fertilizer mass and elemental delivery across common NPK grades when mixed to a 100 ppm Nitrogen target in 10 Liters of water:

NPK Grade Ratio Class Required Mass (10L @ 100ppm N) Elemental P Elemental K
NPK 10-10-10 Balanced 1:1:1 10.00 g 43.64 ppm 83.02 ppm
NPK 20-20-20 Balanced 1:1:1 (Concentrated) 5.00 g 43.64 ppm 83.02 ppm
NPK 12-4-8 Foliage 3:1:2 8.33 g 14.55 ppm 55.35 ppm

What Is NPK 10-26-26?

NPK 10-26-26 is a low-nitrogen, high-phosphorus and potassium fertilizer analysis containing 10% Nitrogen (N), 26% Phosphate (P₂O₅), and 26% Potash (K₂O). Converting label oxide numbers to elemental mass, 100g of 10-26-26 provides 10.0g of Nitrogen (N), 11.3464g of elemental Phosphorus (P), and 21.5852g of elemental Potassium (K).

Agronomic Utility & Potassium Management

10-26-26 is used late in the season or during reproductive development when crops require phosphate and potash without stimulating excess vegetative leaf flush. Heavy potassium applications require adequate irrigation to prevent osmotic stress and magnesium/calcium uptake competition.

Using This Calculator with NPK 10-26-26

This page pre-loads 10-26-26. To mix for 100 ppm N in 10 L of water, the calculator determines that 10.000 g of 10-26-26 product delivers 100 ppm N, 113.46 ppm elemental P, and 215.85 ppm elemental K.

Agronomic Context & Application Guidelines

Primary Utilities

  • •Late-season ornamental and perennial feeding where reduced nitrogen is desired
  • •Nutrient support for crops with substantial potassium and phosphorus demands
  • •Root and tuber maintenance in media with adequate nitrogen reserves

Limitations & Cautions

  • •Does not force flower initiation on immature plants or plants lacking proper environmental triggers
  • •High potassium delivery requires monitoring to avoid competitive inhibition of magnesium and calcium uptake
  • •Unsuited for early vegetative stages requiring active canopy development

Application Risk Factors

  • •high Potassium competition against Calcium and Magnesium uptake
  • •substrate salt accumulation in dry soils
  • •unsuited for early vegetative foliage development

Common Calculation & Application Pitfalls

  • Believing low-N high-PK fertilizer forces instant blooming
  • Over-applying late in the season in dry soils without adequate irrigation
  • Ignoring calcium and magnesium balance during heavy potassium applications

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Troubleshooting & Diagnostics Guide

1 Leaf tip chlorosis on lower leaves.

Diagnosis: High potassium application competing with magnesium uptake.

Treatment: Confirm media moisture and supply balanced calcium/magnesium supplements if needed.

Glossary of Terms

PPM (Parts Per Million)
A measurement of concentration. For dilute aqueous solutions, 1 ppm is commonly expressed as approximately 1 mg/L.
N-P₂O₅-K₂O
The nutrient-analysis convention used on fertilizer labels for nitrogen, phosphate expressed as P₂O₅, and potash expressed as K₂O.
Half Strength
Using 50% of a fertilizer's label-recommended dose for the same water volume, a common practice for houseplants to reduce the risk of salt buildup in containers.

Frequently Asked Questions

What does NPK 10-26-26 mean?
NPK 10-26-26 means the fertilizer guarantees 10% Nitrogen (N), 26% available phosphate (P₂O₅), and 26% soluble potash (K₂O).
What is the elemental breakdown of 10-26-26?
10-26-26 supplies 10% Nitrogen (N), 11.3464% elemental Phosphorus (P), and 21.5852% elemental Potassium (K).

Scientific References

  1. Source: iowadot.gov