The actual yield is the amount of product you really collect, weigh and bottle at the end of a reaction. It is almost always smaller than the theoretical yield, the maximum predicted by stoichiometry, because reactions stop short of completion, side reactions consume starting material and some product is lost on filter paper, in the separating funnel or during recrystallisation.
If you already know (or can estimate) the percent yield of a procedure – from a published method, from your own previous runs or from a target in a production plan – multiplying it by the theoretical yield predicts the actual yield. This is useful for planning: how much starting material do you need to end up with 10 g of a compound, and how much will a long synthesis really deliver?
For multi-step syntheses the yields multiply. Three steps of 85%, 92% and 78% give an overall yield of only 61%, which is why chemists try hard to keep routes short. Switch to the multi-step mode, list the yield of each step and the calculator returns the overall yield and the final mass.
How to use the Actual Yield Calculator
- Yield given as
- Theoretical yield
- Percent yield
- Percent yield of each step (%)
- Molar mass of the product (optional – for moles)
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Enter the theoretical yield and the percent yield (or the list of step yields). The calculator multiplies them, subtracts to find the product lost and, if you give the molar mass of the product, converts both yields into moles.
Worked example
A synthesis of aspirin (M = 180.16 g/mol) has a theoretical yield of 12.5 g, and the procedure normally gives 82%. The expected actual yield is 12.5 × 0.82 = 10.25 g (0.0569 mol), so about 2.25 g is lost along the way.
If the same 12.5 g theoretical yield came from a three-step route with step yields of 85%, 92% and 78%, the overall yield would be 0.85 × 0.92 × 0.78 = 0.610, i.e. 61.0%, and the actual yield only 12.5 × 0.610 ≈ 7.62 g.
Overall yield of multi-step routes
| Yield per step | 3 steps | 5 steps | 10 steps |
|---|---|---|---|
| 95% | 85.7% | 77.4% | 59.9% |
| 90% | 72.9% | 59.0% | 34.9% |
| 80% | 51.2% | 32.8% | 10.7% |
| 70% | 34.3% | 16.8% | 2.8% |
Tips
- Check the equation is balanced before using coefficients.
- Find the limiting reagent before calculating a yield.
- Keep temperatures in kelvin for rate and equilibrium equations.
- Everything is calculated in your browser.
Common mistakes to avoid
- Using the excess reagent to calculate theoretical yield.
- Including pure solids and liquids in equilibrium expressions.
- Entering temperatures in °C into the Arrhenius equation without converting.
Inputs explained
| Field | What to enter |
|---|---|
| Yield given as | Choose one: One overall percent yield, Yields of several steps (multi-step synthesis) |
| Theoretical yield | Units: g, mg, µg, kg, oz, lb |
| Percent yield | In % |
| Percent yield of each step (%) | A list of numbers separated by commas, spaces or new lines |
| Molar mass of the product (optional – for moles) | Units: g/mol, kg/mol, Da (u), kDa |
What each result means
- Actual yield = [Theoretical yield]×[Overall fraction]
- Overall percent yield = ([Overall fraction])×100
- Product lost (theoretical − actual) = [Theoretical yield] – [Actual yield]
Formula
Actual yield = theoretical yield × percent yield ÷ 100 · multi-step: overall yield = Y₁ × Y₂ × … × YₙWorked example
Inputs — Yield given as: One overall percent yield; Theoretical yield: 12.5 g; Percent yield: 82 %; Molar mass of the product (optional – for moles): 180.16 g/mol.
Results — Actual yield = 10.25 g; Product lost (theoretical − actual) = 2.25 g; Actual yield in moles = 0.056894 mol; Theoretical yield in moles = 0.069383 mol.
Key terms
- Actual yield
- The measured quantity of product obtained from a reaction.
- Theoretical yield
- The maximum quantity of product predicted from the limiting reagent and the balanced equation.
- Percent yield
- Actual yield ÷ theoretical yield × 100%.
- Overall yield
- The product of the yields of all steps in a multi-step synthesis.
Frequently asked questions
What is the actual yield?
The amount of product actually obtained and measured after the reaction and purification, as opposed to the theoretical maximum.
How do I calculate actual yield from percent yield?
Multiply: actual = theoretical × percent ÷ 100. For a theoretical yield of 15 g at 70%, the actual yield is 10.5 g.
Why is the actual yield lower than the theoretical yield?
Incomplete reactions, equilibria, side products, mechanical losses during transfers, filtration and recrystallisation, and impure reagents.
Can the actual yield be higher than the theoretical yield?
Only on paper – a product above 100% usually still contains solvent, water or impurities. Dry it to constant mass and weigh again.
How do yields combine in a multi-step synthesis?
They multiply. Five steps of 90% each give 0.9⁵ = 59% overall; ten steps of 90% give only 35%.
How much starting material do I need for a target amount?
Divide the target by the expected fraction: to isolate 8.0 g at 80% yield you must plan for a theoretical yield of 10.0 g, then scale the reagents from that.
What formula does the Actual Yield Calculator use?
Actual yield = theoretical yield × percent yield ÷ 100 · multi-step: overall yield = Y₁ × Y₂ × … × Yₙ.