Bordeaux Mixture Calculator & Copper Sulphate & Lime
Mixes for blight
Mix Bordeaux mixture right — from your spray volume and strength get the copper sulphate and lime, the number of tanks and the per-tank amounts.
Enter your spray
Next: dissolve the copper sulphate in a plastic (never metal) vessel and the lime separately, then combine and spray fresh the same day to fully cover both leaf surfaces. Test on a few plants first.
1% Bordeaux ≈ 1 kg copper sulphate + ~1 kg lime per 100 L; wear gloves, mask & protective clothing.
Bordeaux mixture — key facts
- 1% mixture
- 1 kg copper + ~1 kg lime / 100 L
- Strength
- kg copper sulphate per 100 L
- Common strengths
- 0.5% / 1% / 2%
- Mix in
- plastic or wood, never metal
- Use
- fresh, same day
- Acts
- protectant, before disease
- Controls
- blight, downy mildew, canker
- Privacy
- Runs in your browser; nothing uploaded
The classic copper fungicide, mixed right
Bordeaux mixture has protected vines, potatoes and orchards for over a century — a simple blend of copper sulphate and lime in water that coats the plant and stops fungal and bacterial diseases taking hold. But it only works when mixed correctly: too little lime and the copper scorches the leaves; the wrong strength and you either waste copper or under-protect. Getting the quantities right for your spray volume is the whole game.
This tool gives the exact copper sulphate and lime for your chosen volume and strength (0.5%, 1% or 2%), the number of tanks, and the per-tank amounts so you mix each load accurately. Dissolve the copper and lime separately (in plastic or wood, never metal), combine, and use the mixture fresh the same day. Copper is a heavy metal — use the minimum effective strength, wear protection, and observe limits. Pair it with the Spray & Tank Mix and Pre-Harvest Interval tools.
Mix it right
Exact copper and lime so you avoid scorch and under-dosing.
Per-tank amounts
Know what to add to each tank, not just the total.
Pick the strength
0.5% for tender foliage up to 2% for dormant woody sprays.
Use copper wisely
Minimum effective dose — copper accumulates in soil.
Frequently Asked Questions
How do I make Bordeaux mixture?+
Dissolve copper sulphate in part of the water (in a plastic or wooden vessel, never bare metal), slaked lime in another part, then pour the two together while stirring. A 1% mixture is 1 kg copper sulphate plus about 1 kg lime in 100 litres of water. This tool gives the exact amounts for your spray volume and strength.
What is the Bordeaux mixture ratio?+
Classically expressed as copper sulphate : lime : water, e.g. 1:1:100 for a 1% mixture. The strength (%) is the kilograms of copper sulphate per 100 litres of water; lime is usually equal (ratio 1), but good-quality fresh lime can be a little less. Set the strength and ratio and the tool calculates both.
What strength of Bordeaux mixture should I use?+
Commonly 0.5% for tender foliage, 1% as a general strength, and up to 2% for dormant sprays on woody plants. Lower strengths reduce phytotoxicity (leaf scorch). The tool supports 0.5%, 1% and 2%; always follow local recommendations for your crop and growth stage.
Why add lime to copper sulphate?+
Copper sulphate alone is acidic and scorches plants. Lime neutralises it, forming insoluble copper compounds that stick to the plant and release copper slowly — protective and longer-lasting while gentle on foliage. Too little lime risks scorch; the right balance is what makes Bordeaux mixture work.
What does Bordeaux mixture control?+
It's a broad-spectrum protectant fungicide and bactericide: potato and tomato late blight, downy mildews (grape, cucurbits), leaf spots, anthracnose, citrus and other cankers, and many bacterial diseases. It acts on contact and must be applied before or at the very start of disease, not as a cure.
Why must I use it fresh?+
Bordeaux mixture deteriorates on standing — it thickens, the particles aggregate and it clogs nozzles and loses effectiveness. Always prepare only what you'll spray that day and use it immediately. Don't store the mixed spray. The tool's per-tank amounts help you mix just what each tank needs.
Can Bordeaux mixture damage plants?+
Yes if misused — too strong a mix, too little lime, application in hot sun or on very tender new growth can cause copper scorch (leaf spotting, russeting on fruit). Use the right strength for the growth stage, ensure adequate lime, spray in cool conditions, and test on a few plants first.
Is Bordeaux mixture organic?+
Copper-based fungicides including Bordeaux mixture are permitted in many organic systems, but copper is a heavy metal that accumulates in soil, so use is often capped per year. Use the minimum effective strength and frequency, and check your certification's copper limits. It's a tool to use sparingly, not routinely.
How much area will my mix cover?+
That depends on your spray volume per area (often 500–1,000 L/ha for full cover, less for young crops). Enter the total volume directly, or switch to 'by area' and give your spray volume per hectare and the area; the tool then sizes the copper and lime for the whole job.
What precautions should I take?+
Copper sulphate is harmful — wear gloves, goggles and a mask, mix in plastic/wooden (not metal) containers, avoid spray drift onto water (toxic to fish), keep away from children and livestock, and observe the label's pre-harvest interval. Wash thoroughly after handling.